cdg final t_dversion2

Table of ContentsIntroduction ....................................... . . . . . .............................................................1

Examining a field ................................................. . . . . . . . . . . . . . .................................... 2

Tips for shipping to diagnostic laboratories .......................... . . . . . . . . . . . . .......................... 2-3

Stage I: Scouting from emergence to knee-high ................................. . . . . ........................ 4

Stage II: Scouting from knee-high to tasseling ....................... . . . . . . . ................................ 11

Stage III: Scouting from tasseling to maturity ................................................................ 16

Disease symptoms .......................................................... . . .................................. 24

Leaf diseases ................................................................. . . . . ........................... 24-26

Smutting diseases ...................................................... . . . . ..................................... 26

Virus and virus-like diseases ...................................................... . . . . ......................... 27

Fungal systemic diseases .......................................... . . . ..................................... 27-28

Stalk and root rot diseases ................................................................................. 28-29

Ear and kernel rots ...................................................... . . .................................. 29-30

Insect injury symptoms and management recommendations ....................... . . . . . . . ......... 31-39

Herbicide injury symptoms ........................................................ . . . ...................... 40-42

Herbicides that may be used or trigger symptomology in corn .............. . . . ...................... 43-47

Herbicides listed by active ingredient and mode of action ............................................ 48-51

Nutrient deficiency symptoms ............................................................................. 52-53

Index ................... . . . ......................................................................................... 54

IntroductionThis manual is prepared and distributed by Monsanto Company to help farmers, seed dealers, and company personnel determine the likely causes of abnormal corn plant appearance. While the primary target is the North American Region, the principles and many of the situations described in this publication extend to the regions of the world where corn is grown.

Symptoms may be due to a single cause or the result of two or more interacting factors. Also, because of their different genetic backgrounds, different hybrids may not have identical symptoms in response to the same cause. Routine field examinations are crucial in spotting problems or potential problems. Some growers em-ploy professional crop scouts rather than perform this function themselves. Weekly examinations are generally sufficient.

Once a problem has been identified, its extent and severity must be determined to decide whether corrective action is necessary. Many pest management recommendations include threshold levels when control mea-sures will return a profit. Consult Cooperative Extension Service and chemical company recommendations for control measures.

1 Corn Diagnostic Guide

1Diagnosing Field Problems in Corn

TIPS FOR SHIPPING TO DIAGNOSTIC LABORATORIESTrained, experienced agronomists, crop protection, research, and sales personnel stand ready to assist you in diagnosing field problems. Local seed dealers are your first contact when questions arise. Positive diagnosis often requires identification or confirmation of causes by a diagnostic laboratory. Most states have some arrangement, usually through their Cooperative Extension Service office, for accessing expert diagnosis.

Some of these are more formally conducted than others, and cost of the service varies. Also, there are a few private laboratories that are equipped to provide such services. Your local Cooperative Extension Service office can suggest companies and provide contact information.

When preparing plant or soil samples for a diagnosis, follow these instructions offered by the laboratories.

2

EXAMINING A FIELDCarry the appropriate tools to help effectively scout or monitor fields. Some basic tools to have on hand include:

Tape measure•Knife•Trowel (6 or 8 inch)•Magnifying glass•Clipboard and record keeping materials•

Small plastic bags•Water source•Paper towels•Calculator•Field marking flags•

A spade and a set of nesting pails may be useful if considerable digging is expected. Digital cameras can be helpful in getting a record of insects or disease symptoms.

Be very careful when making area-to-area or field-to-field comparisons. Many factors can influence appearance, including: soil type, slope, and drainage; previous crops; fertility practices; seedbed preparation; date, depth, and rate of planting; pest control; seed lot; and hybrid.

Look for positives, not just problems. Observe and note hybrid differences, as well as the effects of fertilizer and cultural practices.

The following diagnostic key separates plant growth into three primary stages of crop development:

Stage I Emergence to knee-high

Stage II Knee-high to tasseling

Stage III Tasseling to maturity In the field, onset of symptoms might occur earlier or later than indicated, and may be observed during more than one growth stage.

Provide representative samples of each problem 1. observed, as well as a healthy sample from unaffected plants or plant parts.

If sending leaf tissue, place sections of leaves 2. showing disease symptoms between pieces of dry paper toweling or notebook paper.

If sending the whole plant, remove excess soil 3. from the roots and wrap the roots in moist paper toweling. Put roots and towel in a plastic bag. Do not place the entire plant in a plastic bag. Wrap stem and leaves with paper, foil, or cardboard.

Do not add water or crush specimens 4. unnecessarily.

Use a sturdy envelope or box for shipping.5.

Avoid shipping at times that are likely to result in 6. the parcel lying in a post office or freight depot over a weekend or holiday. Overnight delivery, early in the week, is strongly recommended.

Information will need to be provided with the 7. plant specimen. Often, laboratories have specific forms that are required when submitting a sample. Information requested on such forms often includes the following:

Variety (hybrid number) of crop. •

Location where sample was taken • (county, township, and town)..

Date of planting, date problem was • first observed, and date sample was collected. Indicate whether the problem is better or worse than when first

observed. Visit a problem area twice, on dates about a week apart, to determine whether the problem is intensifying, spreading, or disappearing.

Crop symptoms as observed in the field, • such as “plants were wilted” or “leaves appeared spotted.” Describe the size of area affected: spots, strips, or the entire field.

Percentage of plants affected. •

Soil type (clay, sand, muck, etc.). •

Topography around affected plants, such • as high ground, low ground, or gently sloping.

Fertility level (include a soil test report, • if available) and the amount, kind, and timing of fertilizer application.

Pesticides applied (fungicides, herbicides, • insecticides, application rate, and date).

Soil moisture situation at and since • planting. If the field was irrigated, indicate the amount and dates of water application.

Unusual recent air temperatures or • humidity conditions.

Previous cropping and tillage history.•

Types of weeds in the field. •


2Stage I: Scouting from Emergence to Knee-High

4

Determine the extent and severity of any problem identified. Is the problem throughout the field or spotty and localized? Has emergence been completed or are there seeds sprouted, ready to emerge? Take accurate stand counts and determine percent of stand achieved.

If replanting is necessary, take steps to prevent recurrence of the cause for poor emergence. Verify that the planter is operating properly and that fertilizer or pesticide issues have been corrected.

GENERAL SYMPTOM POSSIBLE CAUSE REMARKS

No seed1. Planter •

Rodents or birds•

Improper adjustment; row unit drive not engaged; worn parts; clogged spout; empty box or tank; wrong plates, disks, or drum; excess or wrong seed treatment.

Digging and partly-eaten kernels.

Normal seed 2. appearance; not swelled

Unfavorable soil conditions•

Poor seed-soil contact•

Cold, dry soil.

Inadequate press wheel pressure; improper closing wheel adjustments; inadequate residue management; dry or cloddy soil.

Normal seed 3. appearance; swelled but not sprouted


Fertilizer or pesticide injury•

Cold, wet soil.

Phytotoxic pesticides or too much fertilizer too close to the seed.

Seed dead, rotted4. Seed rots or seedling blights• These are accentuated when soil conditions are unfavorable for germination and seedling growth. Many species of fungi and/or bacteria may be involved. Fungicide seed treatment protects the seed, not the seedling.

% stand achieved = X 100 number of plants establishednumber of seeds planted

If the stand is uneven or if there are skips down the row, dig to find the planted seed and its distribution.


Seed dead, rotted 4. (cont.)

Fertilizer injury•

Insecticide injury•

Dead seed planted•


Fertilizer salts, nitrogen, and potassium draw moisture and may leave seed in soil too dry to support growth. In-furrow applications are more likely to cause fertilizer injury than starter fertilizers placed at least 2 inches from the seed. Ammonia toxicity is caused when planting follows anhydrous or aqua ammonia application too closely or where application was too shallow. This can kill or stunt seedlings. Roots appear sheared off. Boron and some other micronutrients impair germination if they are too close to the seed.

Some soil-applied organophosphate insecticides can impair germination if placed in furrow with the seed. Check the label and apply only as directed.

Cold, dry, wet, or crusted soil.

Seed hollowed out5. Insects• Seed corn beetle, seed corn maggot, or wireworm (see pp. 36-38).

Sprout twisted or 6. leaves expanded below ground


Seed planted too deep•

Mechanical injury to seed in • handling or planting

Chemical injury•

Crusted, cold, or cloddy soil. A cloddy surface can allow light to reach the sprout and trigger leafing too soon. In the case of crusting, rotary hoeing may be beneficial.

Fertilizer (see p. 5); insecticides (see p. 5); or some herbicides such as acetanilides and dinitroanilines (see pp. 41-42).

Slow, uneven 7. emergence

Planter•


Seed planted too deep•

Seed injury due to improper operation or adjustment, including planting depth.

Cold, dry, wet, or crusted soil. In the case of crusting, rotary hoeing may be beneficial. Properly banded fertilizer at planting may help seedlings overcome unfavorable soil conditions.


6


Seedlings pulled 1. or dug up, seed eaten

Bird or rodent damage• Chemical repellents may help.

Slow, uneven plant 2. growth

Unfavorable growing • conditions

Low fertility•

Insects attacking roots•

Nematodes attacking roots•

Chemical injury•

Non-uniform planting depth•

Failure of secondary roots • to develop (rootless corn syndrome)

Cold, dry, wet, or compacted soil. Properly banded fertilizer at planting may help minimize the effects of some unfavorable growing conditions.

If a nutrient deficiency due to inadequate amounts in the soil, is confirmed, consider sidedressing or foliar application, depending on the nutrients involved (see pp. 52-53).

Corn root aphid, corn rootworm, grape colaspis, webworm, white grub, or wireworm (see pp. 31-38).

Requires microscopic analysis.

Fertilizer (see p. 5); insecticides (see p. 5); herbicides such as Balance®; Command® or Scepter® carryover (see pp. 41-42); or liquid manure.

Dry, loose soil is not conducive to normal root development. This condition is accentuated by shallow planting and whipping by wind. Cultivation may help by throwing soil around the base of plants.

Discolored leaves3. Nutrient deficiency•


Magnesium, nitrogen, phosphorus, or sulfur (see pp. 52-53). Nitrogen deficiency results in a yellow discoloration of leaves. Phosphorus deficiency results in a purpling of leaves due to the accumulation of anthocyanins. If nutrient deficiency is confirmed, consider sidedressing or foliar application, depending on the nutrients involved.

Waterlogged, cold, or compacted soil. These conditions can also affect nutrient uptake and translocation.

If plants are abnormal in appearance, try to identify one of the following specific symptoms.

GENERAL SYMPTOM POSSIBLE CAUSE REMARKSDiscolored leaves 3. (cont.)

Insects attacking roots•


Chemical injury•

Wind damage•

Frost or freeze•

Cold (not freezing) • temperature stress

Anhydrous burn•

Mechanical injury•

Hybrid differences•

Most observed leaf discoloration is due to nutrient deficiency induced by damaged or inadequate roots (see nutrient deficiency, above).


Fertilizer (see p. 5); insecticides (see p. 5); herbicides such as Balance®; Command® or Scepter® carryover (see pp. 41-42); liquid manure.

Abrasion by sand or soil particles. Difficulty establishing secondary roots.

Check growing point for damage. Seedlings often recover. Most pronounced in low-lying areas.

Cool nights and warm days promote above-ground plant growth at the expense of root development. This leads to increased demand by the above ground tissues for more nutrients than the roots can deliver. The result can be short-term deficiency symptoms until the root system becomes more developed.

Uneven Corn Plant Growth


8


Leaves rolled or 4. puckered, may be wilted

Drought•

Insects attacking roots or • stalks


Mechanical root pruning•

See Section 6, Insect Injury Symptoms (p. 31-38), plus chinch bug, cutworm, Japanese beetle, stink bug, or webworm.


Leaves rolled or 5. twisted together (“onion leaf” or “buggy whip”)

Herbicide injury•

Temperature variation•

Nutrient imbalance•

Hail damage•

Acetanilides, dinitroanilines, or phenoxys (see pp. 41-42).

Alternating hot and cold weather, inducing very rapid growth spurts followed by little or no growth.

Boron toxicity or calcium deficiency (see p. 52).

Injury to the growing point at this growth stage can result in short-term wrapping of leaves.

Shredded leaves 6. or eaten plants

Wind damage•

Hail damage•

Insects•

Livestock or wild animal • grazing

Armyworm, common stalk borer, corn earworm, cutworm, European corn borer, grasshopper, slug, or webworm (see pp. 32-37).

Look for tracks.

Leaves spotted, 7. striped or dead

Wind damage•

Low soil pH•

Nutrient deficiency •

Insects•

Disease•

Fertilizer or herbicide injury•

Abrasion by sand or soil particles.

Beaded streaking of leaves, which turn reddish-purple and may die.

Boron, copper, magnesium, potassium, sulfur, or zinc (see pp. 52-53).

Flea beetle, leaf miner, or thrips (see pp. 35-37).

Anthracnose, bacterial wilt, eyespot, Goss’s wilt, holcus spot, seedling blights (favored by cool, wet soil), virus or virus-like diseases (see pp. 24-27).

Anhydrous burn; spray drift; foliar-applied herbicides such as Buctril®, Basagran®, Gramoxone®, or Blazer®; Classic®, Scepter®, or Reflex® carryover; premix acentanilides post-applied (see pp. 40-42).



Leaves spotted, 7. striped or dead (cont.)

Sunscald or cold •


Cold nights followed by clear, bright, fast-warming days.

Rows of holes 8. across leaves

Insects• Billbug, common stalk borer, corn borer, cutworm, or stink bug (see pp. 32-37).

Plants wilt and 9. die suddenly

Insects•

Wind damage•

Disease•

Herbicide injury•

Frost or freeze•

Lightning•

Anhydrous burn•

Flooded, water-logged soil•

Billbug, chinch bug, cutworm, stink bug, white grub, or wireworm (see pp. 32-38).

Seedling blights, bacterial wilt, or Goss’s wilt (see p. 26).

Triazines or misapplications of glyphosate herbicides (see pp. 41-42).

Check growing point for damage. Seedlings often recover.

Kills everything, usually in circular area.

“Buggywhip”

Corn plant two days after frost

10


Plants twisted or 10. broken off

Herbicide injury•

Insects•

Especially 2,4-D followed by wind (see pp. 41-42).

Billbug, cutworm, lesser cornstalk borer, or stinkbug (see pp. 32, 36-37).

Inhibited root 11. development or malformed roots

Nematode injury•

Insects•

Fertilizer injury•

Herbicide injury•

Soil conditions•


Corn rootworm, grape colaspis, white grub, or wireworm (see pp. 34-38).

Phenoxys, Banvel®, carryover dinitroanilines, and Scepter® or Classic® carryover (see pp. 41-42).

Planting when soils are too wet can cause sidewall compaction that can arrest or severely restrict corn root development. Look for flat-sided or abruptly arrested root systems.

Wind Damage in Corn Field

Hail Damage in Corn Field


3Stage II: Scouting from Knee-High to Tasseling

This is the period of most rapid plant growth. Nutrient and moisture demands are high; deficiencies will likely reduce crop yield potential. Problems must be evaluated for economic damage potential before control decisions can be made. Observe differences due to hybrids and management practices.

If plants are abnormal in appearance, try to identify one of the following specific symptoms.


Uneven height 1. (tall plants, short plants)

Emerged at different times•

Varied nutrient or moisture • availability under drought conditions

Low soil pH•

Herbicide drift•

Nutrients concentrated at dry • soil surface

Fallow (idle land) syndrome•

Uneven planting depth; uneven soil moisture.

Use of burndown products adjacent to cropped area.

Nutrients are unavailable to the plant.

Phosphorus is unavailable to the plant (see p. 53).

Numerous tillers2. Growing point injury•

Favorable early-season • growing conditions

Low plant population•

Adjacent to open spaces • (population gaps) in the row


Disease•

Mechanical or insect damage.

Optimum moisture, high soil fertility, or both.

Crazy top (see p. 27)

Discolored or 3. dead leaves

Nutrient deficiency• Nitrogen, phosphorus, or potassium (see p. 53).

12


Discolored or dead 3. leaves (cont.)

Fertilizer or herbicide injury•

High temperatures•

Sunscald or cold banding•

Insects•


Frost or freeze•


Barren stalk•

Fertilizer or herbicide on foliage. This tends to be more pronounced at row ends or where overlap application was made.

Noted as scalding or bleaching of top leaves first.


Chinch bug, spider mite, or root-attacking insects, which can reduce nutrient uptake (see pp. 32-37).

Purpling or reddening due to anthocyanin expression in response to accumulation of sugars that cannot translocate to the initiating ear.

Whorl leaves dead 4. (“deadheart”)

Disease•

Insects•

Chemical injury•

Excessive heat•

Bacterial stalk rot (see p. 28).

Billbug, corn borer, or fall armyworm (see pp. 32-33).

More common following a late over-the-top application of certain herbicides.

Temperature exceeding 100°F, depending on moisture availability and genetics of the hybrid.

Leaves spotted 5. or striped

Low soil pH•

Nutrient deficiency•

Chemical injury•

Disease•

Beaded streaking of leaves, which turn reddish-purple and may die.

Boron, iron, magnesium, manganese, nitrogen, or potassium (see p. 52-53).

Herbicides, additives’ reactions, or fertilizers; symptoms may be due to spray drift on foliage.

Bacterial leaf blight, eyespot, Goss’s wilt, holcus spot, leaf blights, Physoderma brown spot, rust, sorghum downy mildew, virus or virus-like diseases (see pp. 24-28).


Leaves spotted or 5. striped (cont.)

Insects•

Wind damage•

Hail damage•

Genetic stripe•

Sunscald or cold banding•

Cereal leaf beetle, corn rootworm beetle, corn blotch leaf miner, flea beetle, spider mite, or thrips; root-damaging insects induce nutrient deficiency or drought symptoms (see pp. 32-37).

Abrasion by sand or soil particles.

Observed only on occasional plants.


Leaves eaten or 6. shredded

Livestock or wild animals•

Insects•

Hail damage•

Wind damage•

Disease•

Look for tracks.

Armyworm, billbug, common stalk borer, corn borer, corn earworm, cutworm, grasshopper, Japanese beetle, leaf miner, slug, or wireworm (see pp. 32-38).

Determine if the growing point survived. If it did not, plant will not produce a tassel. Despite this, ear fertilization may still occur.

Sorghum downy mildew (see p. 28).

Plants stunted, 7. leaves close together with mosaic mottle or streaks; leaves yellow or red

Virus or virus-like diseases• Corn lethal necrosis, corn stunt spiroplasma, maize chlorotic dwarf, or maize dwarf mosaic (see p. 27).

Gray or black galls 8. growing on plants

Disease• Common corn smut (see p. 26).

Stalks spindly, 9. unthrifty, yellow


Excess soil moisture•

Excessive plant population•

Root damage•

Stalk damage•

See pp. 52-53.

Insects, nematodes, chemical, or mechanical.

Insects, disease, or mechanical.

Plants wilted or 10. rolled

Drought•

Root damage•

Stalk damage•


Mechanical or insects; chinch bug, common stalk borer, or corn borer (see pp. 32-33).


14


Top leaves tightly 11. rolled (“buggy whip” or “onion leafing”)

Chemical injury•

Cold soil during seedling • stage

Temperature response or • rapid growth syndrome

Nutrition•



2,4-D and other phenoxy herbicides; Banvel®

(see p. 41).

Alternating hot and cold periods, speeding and slowing plant growth.

Boron toxicity or calcium deficiency (see p. 52).

Plants growing 12. up in a curved “gooseneck”

Recovery after root damage•

Recovery after early season • environmental conditions

Insects (usually, but not limited to corn rootworm larvae), nematodes, herbicides (especially phenoxys), soil compaction, mechanical injury, or wind.

Curled or stubby 13. brace roots

Wind and wet soils•

Dry, hot soil surface•

Wind action•

Plants twisted or 14. growing off at 90˚ angle


Plants leaning or 15. broken off

Wind damage•

Livestock or wild animals•

Root damage•

Insects attacking stalk•

Chemical injury, especially if • followed by wind

Soil compaction•

Poor secondary root • development in dry soil

Disease•

Hail damage•

Especially if soil is wet. Wind can cause greensnap at lower nodes of rapidly growing stalk.

Look for tracks.


Common stalk borer or corn borer (see p. 32-33).

Especially Banvel® or phenoxy herbicides (see pp. 39-41).

Inadequate root development.

Rootless corn syndrome due to weather and aggravated by shallow planting.

Bacterial or Pythium stalk rots (see pp. 28-29).


Plants wilt and 16. die suddenly

Lightning•

Drought•

Disease•

Frost or freeze•

Herbicide injury•

Kills everything, usually in a circular area.

Field areas with low water-holding capacity are first to show stress.

Bacterial or Pythium stalk rots (see pp. 28-29).

Misapplication of glyphosate, glufosinate, paraquat, or other non-selective herbicides (see pp. 41).

Tassel feeding 17. (while in whorl)

Insects• Armyworm, corn leaf aphid, or western bean cutworm (see pp. 32-35).

Tassels proliferated 18. into green cluster of fingerlike branches, excessive tillering, leaves often thick and straplike

Disease• Crazy top (see p. 27).

Tassel proliferated, 19. with stringy black vascular bundles present

Disease• Head smut (see p. 26).

“Greensnap” at lower nodes of rapidly growing corn stalk


16

4Stage III: Scouting from Tasseling to Maturity

This period, which commences with the critical pollination stage, includes grain fill, plant maturation, and death. It also includes the critical stage before harvest when standability and ear retention become concerns. Field observations are essential to detect yield-depressing factors during this period.


Eaten1. Livestock or wild animals •

Insects•

Look for tracks.

Armyworm, corn borer, corn rootworm beetles, grasshopper, or Japanese beetle (see pp. 32-36).

Shredded2. Hail damage•

Wind damage•

Disease• Sorghum downy mildew (see p. 28).

Dead “frosted” 3. appearance

Frost or freeze•

Drought•

Disease•

Insects•

Anthracnose, leaf blights, or stalk and root rots (see pp. 24-26; 28-29).

Corn borer, corn leaf aphid, or spider mite (see pp. 31-33; 37).

Spotted or dead4. Disease•

Chemical injury•

Numerous leaf blights such as anthracnose, eyespot, Goss’s wilt, gray leaf spot, Helminthosporium leaf spot, northern corn leaf blight, Phaeosphaeria leaf spot, Physoderma brown spot, rust, or southern leaf blight (see p. 26).

Especially spray drift.

Discolored 5. sheath

Insects•

Disease•

Corn leaf aphid (see p. 31).

Purple sheath spot caused by saprophytic organisms existing on pollen trapped between the leaf sheath and stalk.

If LEAVES are affected,try to identify one of the following specific symptoms


Red or purple 6. color


Barren plant•

Disease•

Insects•


Anthocyanins develop in response to accumulation of sugars that cannot be translocated to filling grain.

Corn rust, corn stunt spiroplasma, high plains virus, or maize chlorotic dwarf (see pp. 24-27).

Corn borer (see p. 33).

White striping 7. with white, downy growth on upper and lower leaf surfaces

Disease• Sorghum downy mildew (see p. 28).

If SILKS are affected,try to identify one of the following specific symptoms


Eaten off1. Insects• Armyworm, corn earworm, corn rootworm beetle, grasshopper, Japanese beetle, or western bean cutworm (see pp. 32-35).

None visible, or 2. delayed several days after tasseling

Heat•

Drought•

Nutrient deficiency or • imbalance


Insects•

Excessive population for • conditions

Especially nitrogen or phosphorus.

Cold nights occurring just prior to silking.

Corn leaf aphid, fall armyworm, or spider mite (see pp. 31-32; 37).

Trapped, balled 3. within the husk

Drought•




See pp. 52-53.

Cold nights during early silking.


18


Red or green color4. Hybrid differences• Fresh silk color is genetically controlled.

If TASSELS are affected,try to identify one of the following specific symptoms


Failed to emerge1. Drought or heat stress•


Insects•

Especially boron (see p. 52-53).

Aphid stress, corn earworm, or fall armyworm (see pp. 31-32).

A mass of leaves2. Disease• Crazy top, head smut, or sorghum downy mildew (see pp. 27-28).

One or more small 3. ears formed

Genotype by environment • interaction

Most common on tillers.

Kernels develop in 4. tassel

Genotype by environment • interaction

Most common on tillers.

Broken off, stalk 5. tunneled

Insects• Corn borer (see p. 33).

If STALKS are affected,try to identify one of the following specific symptoms


Red or purple 1. color

Mechanical injury to plant•

Barren stalk•


Insects•

Anthocyanins develop in response to accumulation of sugars that cannot be translocated to filling grain.

When corn borers tunnels into a stalk, the area above the point of entry may turn red or purple.


Barren (no ear 2. enlargement)

Drought•

Heat•


Insects•

Silks eaten off prior to • pollination

Disease•

Excess population for • conditions

Tillers•

Timing of silk or pollen shed • disrupted


See pp. 52-53.

Corn leaf aphid or spider mite (see pp. 31, 37).

Corn rootworm beetle and Japanese beetle (see pp. 34-36).

Head smut, mildews, virus or virus-like disease (see pp. 26-27).

Seldom produce a fully-developed ear.

Environmental stress.

Broken below ear3. Wind•

Disease•

Nutrient imbalance•

Insects•

Weather stress•



Delayed harvest•

Plants just prior to tasseling are especially vulnerable to greensnap by wind.

Stalk and root rots (see pp. 28-29).

Excess nitrogen, insufficient potassium (see p. 53).

Southwestern corn borer (see p. 33).

Drought, heat, or other conditions limiting photosynthesis.

Machinery; livestock or wild animals.

Broken above ear4. Wind•

Insects•


Delayed harvest•

European corn borer or fall armyworm (see pp. 32-33).

Machinery; livestock or wild animals.

Multiple ears at 5. one node




20


Multiple ears at 5. one node (cont.)

Cold temperature when ears • formed

Disease•

Insects•

Mildews, virus or virus-like disease (see pp. 27-28).

Results from severe silk clipping by insects such as corn rootworm beetle and Japanese beetle (see pp. 34, 36).

Leaning, but 6. not broken (root lodged)

Wind and wet soil•

Poor root development•

Insects•

Nematode activity•

Disease•


Herbicide injury•


Delayed harvest•


Drought, fertilizer placement, soil compaction, low soil pH, or poorly drained soil.

Corn rootworm and other root feeders (see pp. 34-35).

Stalk and root rots (see pp. 28-29).

Especially potassium (see p. 53).

Especially 2,4-D and other phenoxys (see p. 41).

Machinery, livestock or wild animals

Premature death7. Disease•

Insects•

Frost or freeze•

Severe drought•

Lightning•

Leaf blights or stalk and root rots (see pp. 24-26, 28-29).

Corn borer (see p. 34).

Kills everything, usually in a circular area.

Black mold8. Saprophytic• Buildup on dead stalk tissue under warm, humid weather conditions. Timely harvest will deter.

If EARS are affected,try to identify one of the following specific symptoms


Numerous ear 1. shoots, leafy and barren

Disease• Crazy top, sorghum downy mildew, virus or virus-like diseases (see pp. 27-28).


Soft, glistening 2. smut galls, black and powdery when mature

Disease• Common corn smut (see p. 26).

Poorly filled tips3. Hybrid differences•


Interaction between • population, hybrid, and environment

Insects•

Disease•

Drought•

Unusually favorable growing • conditions after pollination

Suboptimum light, carbon • dioxide, or temperature during kernel fill

Especially nitrogen or potassium (see p. 53).

Silks clipped before pollination. Corn borer, corn earworm, corn rootworm beetle, fall armyworm, or Japanese beetle (see pp. 33- 36).

Foliar disease that reduce photosynthesizing area (see pp. 24-26).

Silks at ear tips were not present when pollen was available

Cob elongates, but rarely fills up tip kernel.

Reduced photosynthesis; tip kernels abort.

Small malformed, 4. light weight


Drought or heat stress•

Plant damage•


Second or third ear on stalk, • or on a tiller

Insect-caused plant stress•

Disease•

Soil compaction•

Especially nitrogen and phosphorus (see p. 48).

Mechanical or disease.

Numerous ear-feeding insects (see pp. 32-38).

Leaf blights, stalk and ear rots, virus or virus-like diseases (see pp. 24-30).

Very short husk, 5. remains tight at maturity; ear tip exposed

Weather•


Usually observed after drought or heat has stopped husk growth, but later favorable conditions permit more normal ear size to develop.


22


Barren (little to no 6. grain)

Disease•

Pollination failure•

Pesticide injury•

Head smut, virus or virus-like diseases (see pp. 26-27).

Drought, heat, or other stress interfered with silk/pollen shed timing; insect (clipped silks or caused tassel to abort); chemical injury (especially by growth regulators like 2,4-D and Banvel®).

Following drift or misapplications.

Pinched ear 7. syndrome

Chilling injury during early ear • development

Also called beer can ear. Ear is reduced to 3-4 inches. Well filled kernels are on bottom third of ear, cob tissue on middle third, and undeveloped tissue on top third.

Dropped8. Drought•



Insect damage to shank•

Weakened shank.

Weakened shank.

Ears usually drop free of husk.

Husk usually remains on the dropped ear; European corn borer (see p. 33).

Scattered kernel 9. set

Lack of adequate viable pollen • when silks are receptive

Silks eaten off before • pollination

Heat or drought at pollination•


Herbicide injury•

Insect or animals.

Phenoxy herbicides or too-late applications of glyphosate (see p. 41).

10. Kernel feeding Insects•

Birds, animals•

Corn borer, corn earworm, fall armyworm, picnic beetle, or western bean cutworm (see pp. 33-35).

11. Rotten (spots or entire ear)

Disease•

Insects•

Birds•

Hail or other mechanical injury•

Ear and kernel rots or Helminthosporium leaf spot (see pp. 29-30; 25).

Corn borer, corn earworm, fall armyworm, picnic beetle, or western bean cutworm (see pp. 33-35). Followed by weathering or disease.

Followed by weathering or disease.

Followed by weathering or disease.



12. Kernels eaten from ear tips

Birds•

Wild animals or rodents•

Insects• Corn earworm, fall armyworm, picnic beetle, or western bean cutworm (see pp. 33-35).

13. Tunnels in ear, cob, shank, or stalk

Insects• Corn borer, corn earworm, or fall armyworm (see pp. 32-33).

If KERNELS are affected,try to identify one of the following specific symptoms


Broken seedcoat, 1. “popped” appearance

Genetic and environment • interaction

Popped kernels usually occur under high temperatures.

Horizontally cut or 2. split seedcoat

Silk-cut• A genetic and environment interaction. Not visible until kernels are shelled from the cob.

Pink or red 3. streaking or lengthwise stripes, especially running over crown

Kernel red streak• Caused by toxin secreted during feeding of wheat curl mite. More pronounced toward ear tip. No detrimental effects are known.

Sprouted 4. especially at base of ear

High rainfall and warm • temperature while ear remained erect on stalk

Usually accompanied by mold.

White streaking, 5. also known as “starburst”

Disease• Associated with Fusarium ear rot.

Barren corn Pinched ear syndrome

24

5 This section will help you identify the common corn diseases based on plant symptoms and conditions. It is not uncommon to have symptoms of several different diseases present at the same time. Symptoms of different diseases may appear similar, particularly during early stages of disease development. Laboratory culturing and microscopic examination may be required to make a positive identification.

Growth stages during which symptoms generally appear are listed following the disease name and are described as follows:

Disease Symptoms

LEAF DISEASESAnthracnose (Stage I, III)

Oval to spindle-shaped water-soaked lesions on youngest leaves turn tan to brown with yellow to reddish brown borders. Heavily infected leaves wither and die. Top-leaf die-back may occur 4 weeks to 6 weeks after pollination, leaving the

lower stalk green. The organism thrives in warm, humid weather. The stalk-rot phase of the organism is of greater concern than the leaf blight phase.

Bacterial Wilt and Bacterial Leaf Blight (Stewart’s Wilt, Stewart’s Disease) (Stage I, III)

Young plants exhibit long, green-gray, water-soaked lesions with wavy margins, accompanied by stunting and wilting which lead to plant death. Cavities may form in stalk near the soil line. Bacterial masses ooze from cut end of infected stalks or leaves.

The more common leaf blight phase appears after tasseling. Leaves are streaked with gray-green to yellow-green lesions, each distinguished by the presence of a flea beetle feeding scar toward the base of the streak. Streaks are long and irregular, turning tan as the tissue dies.

Flea beetles (small, oval, black insects) are the primary carrier. Incidence of the disease is relative to beetle population. Sweet corn tends to be more sensitive than field corn to this disease.

Common Corn Rust (Stage II, III) Cinnamon-brown, powdery, circular-to-elongated pustules (blister-like growths) can occur on any aboveground plant tissue, but especially on both surfaces of the leaves. In contrast, pustules of southern corn rust occur primarily on

the upper leaf surface. Pustules rupture leaf surface and rusty “powder” can be rubbed off with fingers. Pustules become dark brown to black late in the growing season. The organism thrives in moderate to cool temperatures and high humidity.

Stage I Emergence to knee-high Stage II Knee-high to tasseling Stage III Tasseling to maturity

Eyespot (Stage II, III) Small (less than ¼ inch), circular, translucent lesions surrounded by a yellow to purple margin, give a halo effect. Lesions occur on leaves (most commonly as plants approach maturity), sheath and husk. The disease is favored by cool, moist weather.

Goss’s Wilt (Leaf Freckles and Wilt, Nebraska Bacterial Wilt and Leaf Freckles) (Stage I, III)

Young plants wilt and die. Vascular bundles are discolored. More common later-season infections produce dull gray-green to orange lesions forming water-soaked streaks with irregular margins on leaves. Within developing lesions, small, irregular

shaped water-soaked “freckles” appear. Bacterial droplets may ooze from the leaf surface early in the morning. Plant injury, such as from hail or wind damage, enhances infection.

Gray Leaf Spot (Stage III) Gray to tan, rectangular lesions on leaf, sheath or husk tissue. Spots are opaque and long (up to 2 inches). Lower leaves are affected first, usually not until after silking. The organism thrives in extended periods of warm, overcast days and

high humidity. It has become more prevalent with increased use of reduced tillage and continuous corn.

Helminthosporium Leaf Spot (Northern Leaf Spot) (Stage III)

Numerous races of the organism have been identified. Symptoms vary by race. Lesions tend to be oblong to blocky, and tan to brown in color. This leaf spot may also cause a black, charred-appearing ear rot. It prefers moderate temperatures and high humidity.

Holcus Spot (Stage I) This organism causes small, circular to oblong, water-soaked lesions toward tips of lower leaves. Later, lesions become creamy white to tan, then light brown with reddish margins. Holcus spot is very similar in appearance to paraquat

damage. Rainstorms accompanied by wind splash overwintering bacteria from the residue onto young plant leaves. This organism does not cause serious loss.

Northern Corn Leaf Blight (Stage II, III) Long (up to 6 inches), elliptical, gray-green lesions that become tan-brown identify infections caused by this organism. Infection spreads up the plant starting on lower leaves. It is favored by high humidity and moderate temperatures. Numerous

physiologic races have been described. Host specific races of the organism may also attack sorghum.


26

Phaeosphaeria Leaf Spot (Stage III) Lesions are initially small, round to oval, pale green or yellow, and scattered on leaves of mature plants. Spots become light tan with reddish-brown margins and may coalesce into irregularly shaped lesions. This disease is most prevalent in areas of

high rainfall and moderate temperatures.

Physoderma Brown Spot (Stage I, III) Small yellow spots appear first at the base of the leaf. These spots become brown and combine to form chocolate-brown to reddish irregular blotches, sometimes as bands of infection across leaf blades. Sheath, husk, tassel, stalk, and leaves

may exhibit symptoms late in the season. Infected stalks may break at a node. This organism is favored by warm, wet weather.

Southern Corn Leaf Blight (Stage II, III) The most common race, named “O,” produces small, elongated (up to 1 inch long), parallel-sided lesions that are tan with brownish borders. This blight primarily attacks leaves. It is favored by high humidity and warm temperatures.

Southern Corn Rust (Stage II, III) Small, circular, orange-to-light-red pustules (blister-like swelling) occur on leaves, especially the upper surface, and sheaths. Pustules rarely break the leaf surface. (In contrast, common corn

rust pustules attack upper and lower leaf surfaces and readily break through the epidermis.) This organism is favored by warm, humid weather.

SMUTTING DISEASESCommon Corn Smut (Boil Smut, Blister Smut) (Stage I, II, III)

Local infection of any plant part, even below the soil surface, occurs through plant wounds or thin-walled cells of actively growing tissue. Resulting

galls are first silver-white, then become gray to black powdery masses of smut spores that are released when the galls break open. Galls on leaves seldom develop beyond pea-size and tend to harden and dry without rupturing. High fertility and plant injury favor the disease. Common smut is not toxic to animals.

Head Smut (Stage III) Seedling infection results in systemic development of the disease as the plant grows and develops. Tassels of affected plants may multiply as a mass of leaves or be replaced by a black, smutty mass which ruptures to release spores, leaving black, thread-like

vascular strands. Ears may be completely replaced by similar, often triangular-shaped, smut masses. Occasionally, part of an ear escapes and produces a few kernels. Hot, dry soil at seedling stage favors infection. One type of head smut also attacks sorghum.

VIRUS AND VIRUS-LIKE DISEASESCorn Lethal Necrosis (CLN) (Stage II, III)

Mosaic patterns appear on leaves and husk. Leaves die from the margins inward and plants may die prematurely. The organism generally starts at the tassel and works downward. Barrenness or sharply reduced grain production is common.

CLN is caused by synergistic interaction when plants become infected by maize chlorotic mottle virus and either maize dwarf mosaic virus or wheat streak mosaic virus. Presently, the disease has been identified only in parts of Kansas and Nebraska.

Corn Stunt Spiroplasma (CSS) (Stage II, III) Corn stunt is caused by a spiroplasma, not a virus. Margins of whorl leaf turn yellow followed by reddening of older leaves and yellow striping which runs the length of leaves. Plants are stunted, have multiple tillers and produce numerous small

ear shoots. Root systems are reduced. Corn stunt symptom development and epidemiological patterns are similar to those of virus diseases.

High Plains Virus (HPV) (Stage I, II, III) Symptoms begin as small yellowish flecks which often appear as lines running parallel to leaf veins. Infected seedlings turn bright yellow and quickly die. Plants may be stunted, older leaves may become red and then necrotic, and ear and

kernel size may be reduced. Considerable symptom variation exists among cultivars. It is spread by the wheat curl mite.

Maize Chlorotic Dwarf Virus (MCDV) (Stage II, III)

Younger leaves are yellow and finely striped. There is a general yellowing or reddening of leaves and plants are stunted. Most affected plants are barren. MCDV is spread by leafhoppers from infected Johnsongrass and other host species. MCDV is

detected more frequently and is more damaging than maize dwarf mosaic.

Maize Dwarf Mosaic Virus (MDMV) (Stage II, III)

Mottling of younger leaves progresses into narrow, light-green to yellowish streaks along leaf veins. Leaves, sheaths and husks may show symptoms. Plants are stunted and ear size and seed set are reduced. Sometimes, multiple tillers or ear shoots

develop. MDMV is most prevalent in areas where Johnsongrass grows and serves as a winter host for the virus. It is spread by aphids.

FUNGAL SYSTEMIC DISEASESCrazy Top (Stage II, III)

Plants have excessive tillering with rolling or twisting of newer leaves. The tassel becomes a mass of leaves; ears, if present, often do likewise. Leaves are usually narrow, thick and appear strap-like. Occasionally over-sized plants will develop.

Infection occurs when young plants are under flooded soil conditions; therefore, it is more frequent in low-lying areas. This is one of numerous downy mildews that attack corn.

UGA1235014

536657


28

Sorghum Downy Mildew (Stage II, III) Leaves are yellow with white stripes; plants are stunted and ears and tassels multiply into leafy masses. Often the base of leaves are chlorotic and sharply contrast with healthy green leaf tips. White, downy growth appears on either or both

leaf surfaces. Leaves often split or shred. This is primarily a disease of sorghum.

STALK AND ROOT ROT DISEASESStalk rots are diseases that are most commonly expressed as plants reach maturity. Stalk rot of corn tends to be a complex of several disease-causing fungi and sometimes bacteria; seldom will only one causal organism be isolated and identified. Plants with rotted stalks almost always have rotted roots, too. Usually, but not always, the same causal organisms are involved. Visual identification is very difficult.

Typically, wilting is the first sign of stalk rot in a field. In a few days, leaves turn a “frosted” gray, ears droop and the outer rind of the lower stalk turns brown. Fields where stalk rot is developing should be harvested early to reduce grain losses.

Anthracnose Stalk Rot (Stage II, III) Early infection may kill plants before pollination, but onset usually occurs just before plants mature. Sometimes a portion of the plant above the ear blanches and dies prematurely (top dieback). Usually, the entire plant is killed and several

nodes are rotted. Late in the season, a shiny black discoloration develops in blotches or streaks on the stalk surface, especially on lower internodes. Internal stalk tissue may become black and soft, starting at the nodes. Lodging typically occurs higher on the

stalk than with other stalk rots. The same organism causes leaf blighting earlier in the season.

Bacterial Stalk Rots (Stage II, III) At least two organisms have been identified as causing bacterial stalk rot. With either, there is rapid development of a soft rot of stalks, accompanied by wilting and plant death. Stalks twist and collapse while still green, disintegrating into a soft

mass often accompanied by a foul odor.

Charcoal Rot (Stage III)Charcoal rot can be expected when the crop has grown under hot, dry conditions; it also attacks sorghum and soybeans. Lower internodes are affected, causing premature ripening, shredding, and crown disintegration. Vascular

strands remain intact but are black or “charred” in appearance. Stalks become gray-black or charcoal color.

Diplodia (Stenocarpella) Stalk Rot (Stage III)Lower internodes are straw-brown, spongy, and dry. Pith disintegrates, leaving vascular strands intact. White fungal growth may appear on the stalk surface. Minute, dark bodies embedded just under the stalk surface are difficult to remove.

5361254

Fusarium Stalk Rot (Stage III)Rotting of roots, crown, and lower internodes leads to premature ripening and stalk breakage. Split stalks may show whitish-pink to salmon color. Disintegration starts at the nodes.

Gibberella Stalk Rot (Stage III)Affected plants wilt, leaves turn dull gray-green, and the lower stalk softens and becomes straw colored as plants die. Pith tissue disintegrates, leaving only vascular strands. The inside of a rotted stalk is pink to red. Small, dark bodies are superficial on

the lower stalk surface and can be scraped off easily.

Pythium Stalk Rot (Stage II, III)This organism attacks individual plants in localized areas, sometimes before flowering. It is usually confined to the first internode above the soil line, where rind and pith develop wet rot. Stalks twist and collapse. Hot, wet weather favors development of this stalk rot.

Red Root Rot (Stage III)Red root rot often occurs in plants that are also stalk rotted. Seminal roots are most damaged and adventitious root damage increases with their age. The root color of affected plants ranges from pink to royal red, with higher soil

temperatures resulting in darker pigmentation. The role of this root rot in stalk lodging is not fully understood.

EAR AND KERNEL ROTSThese rots can affect ears, kernels, or cobs, reducing test weight and grain quality. Some rots are responsible for development of mycotoxins that may contaminate grain. Positive identification is difficult. Rotting observed in the field is often due to a complex of causal organisms, not just one.

Most ear rots are favored by late-season humidity. Infections are increased by ear damage by birds or insects and by stalk lodging that allows ears to come into contact with the soil.

Aspergillus Ear and Kernel Rot (Stage III)Greenish or yellowish-tan discoloration occurs on and between kernels, especially near the ear tip. Symptoms are more prevalent if the husk does not cover the ear tip. The rot is favored by hot, dry weather. It may produce aflatoxins.

Cladosporium Ear Rot (Stage III) Dark gray to greenish black fungal growth causes kernels to appear blotched or streaked. Initial discoloration appears where kernels are attached to the cob. Infection eventually progresses upwards and

infected kernels can be seen scattered over the ear. If completely colonized, ears are dark and lightweight. This disease is often associated with damage due to insects, hail, or frost.

Healthy stalk, left. Diseased stalk, right.


30

Diplodia (Stenocarpella) Ear Rot (Stage III) Symptoms include bleached husks, white mold over kernels, and rotted ears with tightly adhering husks. Early infection (2 to 4 weeks after silking) is likely to lead to complete ear rotting. Later infections may result in partial rotting, usually

beginning at the base. Since corn is the only known host, this disease is most severe when corn is planted following corn in reduced tillage situations.

Fusarium Kernel or Ear Rot (Stage III)

Scattered individual or groups of kernels show whitish-pink to lavender fungal growth. Infected kernels may also have a “starburst” pattern of white streaks on the cap of the kernel or along the base. Infections are more frequent on damaged ear

tips, and are favored by dry weather. Fusarium rot may produce mycotoxins.

Gibberella Ear Rot (Stage III)Symptoms include reddish kernel discoloration, usually beginning at the ear tip. Husks may rot and be cemented to the ear. The organism is favored by cool, humid weather, particularly 2 to 3 weeks after silking. It produces several mycotoxins.

Penicillium Ear Rot (Stage III)Powdery green to blue-green mold develops on and between kernels. Infection usually begins at the ear tips and primarily occurs on ears with mechanical or insect damage. Infected kernels may become bleached and streaked. “Blue eye”

occurs when the embryo becomes discolored due to the presence of blue-green fungal spores and can occur if infected grain is stored at high moisture levels.

Trichoderma Ear Rot (Stage III)Dark green fungal growth is found on and between kernels and husks, often covering the entire ear. The disease usually occurs on ears with mechanical or insect damage. Infected plants tend to be widely distributed within a field.

Photo Citations:

Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org (viewed 9/22/10); Corn Stunt 1235014

William M. Brown Jr., Bugwood.org (viewed 9//22/10) High Plains Virus 5366657

Howard F. Schwartz, Colorado State University, Bugwood.org (viewed 9/22/10) Bacterial Stalk Rot 5361254

Holcus spot and Pythium stalk rot photos courtesy of Don White at University of Illinois

6Insect Identification, Injury Symptoms, & Management Recommendations

APHIDS(1) Corn Leaf Aphid

This small, soft-bodied, bluish-green to gray insect colonizes on or in the whorl, upper leaves, and tassel, especially under dry conditions. It sucks plant juices and can cause wilting, pollen shed failure, and barrenness. The aphid secretes a sticky

honeydew that may gather dirt and act as a medium for mold. Predatory insects, like the lady beetle, may be present and are important predators of aphids. Scouting should occur during late whorl to early

tassel. Aphid infestations after 50% pollen shed have little effect on grain yield. A rescue application of insecticide may be warranted if 50% or more plants have light to moderate infestations and the crop is under moisture stress.

(2) Corn Root AphidThis pinhead-sized, soft-bodied, blue-green to gray-green insect, may be winged or wingless. Corn root aphid groups are found in clusters on the crown and along the roots of young plants. They suck plant juices and cause wilting, discoloration, and stunting. Cornfield ants are generally found in conjunction with corn root aphid colonies. There are no rescue treatments for corn root aphid. Cultural practices like crop rotation and tillage can be effective preventative tactics.

Only the most common or the most economically –damaging corn insects in the North American region are discussed in this chapter. Most, but not all, insect identifications can be made in the field by trained individuals.

As insects progress through their life cycles, they change form and features. The following comments describe the appearance of damaging stages, which may not correspond with their appearance when damage is being investigated. It is not uncommon to investigate crop insect damage, but find none of the suspected insects. At other times, damage from insect feeding may be detected, but the insect is no longer present.

Use economic thresholds whenever possible and seek further pest management guidance if symptoms are unclear. Generalized thresholds for most pests are provided in this guide. These thresholds may change depending on the cost of a control tactic or the commodity value. Always confirm that pest numbers have been suppressed below thresholds following the application of a rescue tactic. Pesticides may perform below expectation due to environmental, chemical, or biological situations, or due to application timing.

While this publication is focused on in-season diagnostics and treatment options of insect pests of corn, a number of Bt traits are available for several of the insect pests discussed in this handbook. The Corn Insect Control with Monsanto Corn Insect Traits and Seed Treatments table (see pp. 39) provides a list of some of these products as well as the insects they control. These products provide season-long control of the specific insects and reduce the need for additional pest management action.


32

ARMYWORMSFall Armyworm

The fall armyworm grows up to 1.5 inches long and appears greenish-brown in color with an inverted white “Y” on its head. It chews ragged holes in the leaves and usually concentrates in the whorl of young plants.

The fall armyworm also feeds on the tassel and bores into developing ears. Early detection is critical since this pest feeds in protected areas of the plant. It lays round, gray eggs in clusters of 50 or more, which are usually covered with scales. Eggs hatch in 3 to 5 days and larvae migrate to the whorl and adjacent plants. Consider using a rescue application if eggs are present on at least 5% of plants or whorl injury is detected on 25% or more plants. Because larvae feed deep in the whorl of young plants, control with insecticides can be difficult.

(2) True ArmywormThe true armyworm is greenish-gray with orange or pinkish lines along the body. “Armies” migrate from maturing small grains or grass at night. They devour foliage, sometimes leaving only leaf midveins,

and chew silks. Infestations are more frequent in no-till or reduced tillage systems and the true armyworm is usually only an occasional pest in rotated corn. Consider an insecticide application if 35% or more plants in the field are infested.

BILLBUGThis black or gray hard-shelled snout beetle is active only at night. Leaves are punctured while still rolled in the whorl. When they unfurl, irregular rows of holes appear across the leaves. The billbug also chews into plant stems at

or below ground level. This feeding can damage the growing point and cause plants to be bent, twisted or stunted and sometimes die. Billbug incidence is often associated with nutsedge. Consider spraying for billbug if stand loss during seedling stages exceeds 5%.

CEREAL LEAF BEETLEThe adult is a 0.2 inch long, hard-shelled beetle with metallic blue-black head and wing covers, and reddish- orange legs and thorax. Feeding on corn is rare and usually limited to field borders. Though the beetle eats completely through the leaf between the veins, plants normally outgrow the injury and rescue applications are not necessary. Generally infestations are limited to Michigan, Indiana, and eastward.

CHINCH BUGThe adult is 0.25 inch long, and is red and black with white wing covers. When crushed, this bug emits a distinct odor. It migrates from grasses and maturing small grains, attacks field borders first and is most destructive during dry years. The

young nymph (juvenile stage) is bright red, but turns black as it develops. Chinch bugs cluster in groups behind the sheath of lower leaves, sucking plant juices and causing wilting and eventual plant death. Management may be necessary if 10 or more chinch bugs are found on more than 50% of plants. Insecticide applications may be limited to only the infested area.

COMMON STALK BORERThis purplish-brown larva may reach 2 inches in length. It has white longitudinal stripes with a distinct purple saddle near the middle of the body. It tends to move out of weedy or grassy field borders and attack

UGA1234011

5364223

corn on field edges (or throughout no-till fields). The larva tunnels into stalks or whorls. Infestation of plants at the 4-7 leaf stage can lead to dead heart. Whorl feeding results in leaves that have a ragged appearance with injury appearing as a series of holes across the leaf. Timing insecticide applications prior to borer tunneling is critical. Consider treating if 10% of V2 plants, 15% of V4 plants, or 30% of V6 plants show symptoms.

CORN BORER(1) European Corn Borer

This larvae varies in shades of tannish-gray and ranges in size from less than 0.5 to 1.0 inch long. There are

two or more generations per season. Larvae of the first generation feed on leaves before they burrow into the stalk. This feeding causes broken midribs and creates a “shot hole” appearance as leaves grow out of the whorl. Consider treating first generation populations if the moth flight has already peaked and 5% or more of plants have shot hole feeding. Second generation larvae feed on and bore into stalks, tassels, ear shanks, and ear tips causing top breakage, ear drop (with husk attached), stalk lodging, and kernel damage. Treatment for second generation larvae may be necessary if more than 10% of plants have fresh or hatched egg masses, or young larvae in the leaf axils. Timing insecticide applications prior to insect tunneling is critical.

(2) Southwestern Corn BorerThis larvae is white or cream-colored and 0.5 to 1.0 inch long. It has distinct black spots except on the overwintering form. Two generations feed on corn. The first feeds on leaves and creates a “shot hole” effect or “dead heart” in very young plants. Later

instars tunnel in the stalk. The second generation larvae feed on developing ear tissue, bore into the shank and ear, and tunnel in the stalk below the ear zone. In the fall, overwintering larvae migrate to the base of the stalk and prepare overwintering

tunnels in the stalk below soil level. These larvae girdle the plants near the soil level, resulting in severe stalk lodging. Treatment may be necessary for first generation populations when greater than 35% of plants hold larvae or show symptoms. Insecticide applications for both first and second generations must be applied before they begin tunneling. Consider a rescue treatment for second generation if eggs or young larvae are found on 20 to 25% of plants.

CORN EARWORMThis larva varies in color from green, yellow, brown

to pink, but all have a yellow-brown head and reach full size at about 1.5 inches. Since the insect is cannibalistic, two or more full-size larvae are seldom found together.

They may feed on leaves in the whorl, on the tassel or on silks, but the preferred feeding site is ear tips and on developing kernels. Moreover, ear injury often leads to ear molds and rots. The window for effective treatment is the few days after eggs are laid and before larvae tunnel into the silk channel.


CORN ROOTWORM This small, white larva feeds on and tunnels into roots or crowns of young plants. It destroys root systems, can delay development, and causes root lodging. Lodging is accentuated by wind storms. Plants may “gooseneck” across rows

and resume upright growth. Rescue treatments for control of corn rootworm larvae are available, but efficacy is greatly dependent on the product’s ability to move into the root zone. Continuous corn

or observations of adult beetles made the previous year can trigger the use of control tactics. The adult beetle may feed on corn leaves, stripping spots

of the upper surface away. After pollen shed, it feeds on pollen and fresh silks. Heavy silk feeding can reduce or prevent pollination and result in partial or complete failure of kernel set. The beetle can be found in ear tips as maturity approaches. The general guideline for silk clipping insects is as follows: control may be necessary if silks are clipped to less than 0.5 inch and fewer than 50% of plants have been pollinated. Also, one beetle per plant in late summer is a useful guideline for justifying whether a control tactic may be necessary to prevent larval injury in continuous corn.

(1) Mexican Corn RootwormThe adult beetle is light green and looks similar to the northern corn rootworm beetle, but can be distinguished by a black stripe on the leg.

(2) Northern Corn RootwormThe adult beetle is less than 0.5 inch long, tan or

green to greenish-yellow without distinctive spots or stripes.

(3) Southern Corn RootwormThe adult beetle is 0.25 to 0.5 inch long, yellow or greenish with six black spots on each wing cover.

(4) Western Corn Rootworm

The adult beetle is about 0.25 inch long, black and

yellow striped or black with a yellow tip on the wing cover. It cannot be visually identified as to species.

CUTWORMThere are many species of cutworms that attack corn and other crops such as cotton, tobacco, and many vegetable crops. Cutworms are widely distributed; some species migrate to Corn Belt states from the South and many overwinter there. Young larvae typically feed on leaf margins and larger larvae feed below or at the soil surface. They chew into or

34

Corn rootworm feeding

completely cut young stalks, causing wilting or death. Plants may recover if injury is limited to above the growing point. Cutworms are primarily active at night. An insecticide application should be considered if 2 to 3% of seedling plants are wilted or cut and larvae are early in their development (<0.75 inch). If larvae are larger, increase the economic threshold to 5% of plants wilted or cut. Plants at V5 or later stages of development usually are unaffected by cutworms.

(1) Black Cutworm The black cutworm larva varies from almost black to lighter gray and is a pest of many crops at the seedling stage. Most of the Corn Belt is re-colonized each year with migrant adults. Cutting is usually observed 300 degree days (base 50°F) after heavy adult

activity. Several generations per year are possible, but the first generation in spring is most injurious. Areas of high soil moisture or low-lying areas within a field are most favorable for this insect and should be scouted first.

(2) Western Bean CutwormThe western bean cutworm affects corn during reproductive stages. The young larva has a pale body with longitudinal brown stripes along the back. Fully grown, it is light brown to

pale gray with a brown head. The cutworm feeds on silks and chews into husks and developing ear tips of the ear shank. Severe ear and kernel damage can lead to mold and ear rots. This insect has historically been limited to the western Great Plains, but has moved eastward and can now be found in many areas of the Corn Belt.

(3) Other CutwormsThe bronzed, claybacked, dingy, glassy, sandhill, and variegated cutworms are less frequent pests and less injurious to corn.

FLEA BEETLEThe flea beetle is a tiny, shiny, black beetle that jumps like a grasshopper when disturbed. It feeds on leaves of young plants and produces “scratch marks” or small holes. The flea beetle is the primary vector of the bacterium that causes bacterial

(Stewart’s) wilt of corn. Consider treating field corn if five or more beetles per plant are found on V4 or younger corn and adverse growing conditions have slowed corn growth. Current seed treatments generally provide good control.

GRAPE COLASPIS This white, curved, grub-like larva develops six distinct foreleg projections. It feeds on young corn roots and can cause nutrient deficiency symptoms.

GRASSHOPPERSeveral species of grasshoppers attack corn. The grasshopper generally moves from field-side hatching sites. It eats leaves from the margin inward and may

prevent pollination by clipping silks. The grasshopper may also chew on tassels, husks, stalks, or kernels. Defoliation and ear damage should be used to determine if an insecticide treatment is necessary in field corn. It may be more economical to limit applications to infested areas like field margins.


UGA4709020

36

JAPANESE BEETLEThis shiny, green-bodied adult beetle has copper- to bronze- colored wing covers. As an adult, it grows to about 0.5 inch in length and feeds on corn leaves and silks. Leaf feeding by this pest appears skeletonized or “lacy.” Larvae are white

with a brown head and feed unobtrusively on the roots of plants. They can be differentiated from other white grubs by the V-shaped pattern of bristles on the raster. The general guideline for silk clipping insects, such as an adult Japanese beetle, is as follows: control may be necessary if silks are clipped to less than 0.5 inch and fewer than 50% of plants have been pollinated.

LEAF MINERThis small, white larva or maggot tunnels between leaf surfaces, leaving long blotchy tunnels within the leaf. This pest seldom reaches economic proportion in corn.

LESSER CORNSTALK BORERThis black larva with white bands burrows into the stalk base of young plants. This borer causes wilting and plant deformities like twisted, bent or often barren plants.

PICNIC BEETLE (Sap Beetle, Scavenger Beetle)This small, dark beetle usually has four orange or

cream colored spots on wing covers. It frequently inhabits ear tips as corn approaches maturity and often appears where primary insect pests or birds have damaged ear tips.

SEED CORN BEETLEThis small, 0.25 to 0.33 inch long brown ground beetle damages the germ and hollows seed before it germinates. The beetle also attacks emerging seedlings, causing spotty stands. Damage is greatest if germination has been delayed by the environment. Current seed treatments generally provide good control.

SEED CORN MAGGOTThis yellowish-white spindle-shaped larva, is about 0.25 inch long and may eat the entire kernel before it germinates. Often times it leaves only the seed coat behind. Wet, cold, and heavy soils are associated with this pest that can create spotty,

uneven stands. Modern seed treatment provides good control. Otherwise, there is no rescue treatment for seed corn maggot and replanting may be the only option.

SLUGThis soft-bodied, slimy and legless grayish creature hides under residue. It is active at night and leaves a telltale silver-colored slime trail on the soil surface. It feeds using a rasping action on the lower stalk and leaves of young plants. This feeding often

removes only one surface of a leaf and the symptom is more common in no-till systems. Insecticidal baits are available for slug control, however, injury seldom warrants this expense.

UGA2511032

SOUTHERN CORN LEAF BEETLEAdult beetles are dark brown and can be difficult to find in the field because they are often covered with soil. Beetles feed on stems and on the edges of leaves of seedlings. Injured plants appear ragged. When beetles feed in large numbers, plants may die. This beetle is most problematic in fields that have not been cultivated.

SPIDER MITETwo species can cause severe damage to corn: banks grass mite and two-spotted spider mite. Spider mite problems are more prevalent when temperatures are high and humidity and rainfall are low. The tiny (about the size of a pencil dot), eight-

legged creature feeds by piercing individual leaf cells and sucking out the contents. Damage is usually first noted as plants approach tasseling and continues through grain dent stage. Lower leaves appear blotched and chlorotic and continued feeding can cause leaves to die. Damage symptoms progress up the plant with time. The mite spins a white web on the leaf surface where it feeds.

STINK BUGSeveral species of green or brown stink bugs occasionally attack corn. The adult (shield bug) has a hard, angular back and wing covers, and gives off a foul odor if crushed. It inserts its piercing-sucking mouthparts into the base of young plants and can kill

the growing point or distort further growth.

SUGARCANE BORERThis tan larvae has indistinct brown spots on each segment. It feeds in whorl-and reproductive-stage plants similar to the southwestern corn borer, except that it does not girdle the stalk. Yield losses occur

due to reduced ear weight. The sugarcane borer is found in Florida, Louisiana, Mississippi, and Texas.

THRIPSSeveral species of this tiny, slender insect occasionally feed on leaves of young corn plants. As an adult, it develops wings. With mouthparts fitted for rasping and sucking, thrips remove the green surface layer in tiny streaks. Individual leaves have a speckled appearance and fields, or affected areas, may look silvery.

WEBWORMThe garden webworm and sod webworm attack young corn. It appears as a gray to yellow-green, spotted, bristly larva about 1 inch long. This pest gets its name from the fine web it spins from its silk-lined underground nest. The larva uses this web to travel to plants at night and return to its nest during the day. Similar to the cutworm and wireworm, the webworm’s primary feeding site is at or just below the surface. Injury becomes more obvious as damaged leaves emerge from the whorl. Larvae also feed on the underside of lower leaves.

WHEAT CURL MITE (Kernel Red Streak)

Kernel red streak is caused by a toxin secreted during feeding of the wheat curl mite. It is most common on yellow corn, but may occur on sweet corn, popcorn, and white corn. Streaks are more pronounced toward ear tips, especially if kernels are exposed.

Streaks vary from dark red on yellow kernels to pink on white kernels. No detrimental effects from the discoloration are known.


38

WHITE GRUBThe larva has a thick, soft body with three pairs of legs just behind a brown head. It ranges from 0.125 to 1.5 inches long depending on age, and it characteristically curls into a “C”-

shape when disturbed. There are several species with 1 to 4 year life cycles. The white grub feeds on developing roots of young plants, and causes stunting, nutrient deficiency symptoms and death. Heaviest infestations occur where corn is planted into killed sod. There are no rescue treatments for grubs and the percent stand loss is the best gauge for determining if replanting is worthwhile.

WIREWORMThe larva is shiny and slender with a yellow- to brown-colored hard body. It ranges in size from 0.5 to 1.5 inches long, depending on age and species.

Damage to seed or young plants reduces stand and vigor. It damages the germ, stunts plants by root pruning or kills the growing point by boring into the base of the stem near ground level. Modern seed treatments prevent damage to seeds. Like

grubs, there is no way to combat this pest after stands have been thinned. Use percent stand loss as a gauge for determining if replanting is worthwhile.

Photo Citations:

Frank Peairs, Colorado State University, Bugwood.org (viewed 9/23/10) Armyworm 5364223

Clemson University - USDA Cooperative Extension Slide Series, Bugwood.org (viewed 9/23/10) Billbug 1234011

University of Georgia Archive, University of Georgia, Bugwood.org (viewed 3/11/2011) Grasshopper 4709020

David Riley, University of Georgia, Bugwood.org (viewed 9/23/10) Lesser Cornstalk Borer 2511032

Alton N. Sparks, Jr., University of Georgia, Bugwood.org (viewed 3/11/2011) White grub (scarab) 1327103

Corn earworm damage

Be

low

Gro

un

d

Western corn rootworm larvae Trait Trait Trait NC

Northern corn rootworm larvae Trait Trait Trait NC

Mexican corn rootworm larvae Trait Trait Trait NC

Wireworm (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

White grubs (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Grape colaspis (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Seedcorn maggot (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Color Key to Activity Insect activity conferred by:

= Control Trait, Insecticide 250 rate, or multiple

= Suppression Trait, Insecticide 250 rate, or multiple

= No Control NC = No Control

Protection for Above and Below Ground PestsProtection for Above Ground

Pests

Trait NameGenuity®

SmartStax®

Genuity® VT Triple PRO™

YieldGard VT Triple®

Genuity® VT Double PRO™

Trait Logo

Seed Treatment Poncho® 250

Insects

Ab

ove

Gro

un

d

European corn borer Trait Trait Trait Trait

Southwestern corn borer Trait Trait Trait Trait

Corn earworm (ear feeding) Trait Trait Trait Trait

Western bean cutworm Trait NC NC NC

Black cutworm Trait/250 Rate 250 Rate 250 Rate 250 Rate

Fall armyworm Trait Trait Trait Trait

Sugarcane borer Trait Trait Trait Trait

Common stalk borer Trait Trait Trait Trait

Lesser cornstalk borer Trait Trait Trait Trait

Corn flea beetle (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Corn leaf aphid (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Chinch bugs (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Southern corn leaf beetle (seedling stage) 250 Rate 250 Rate 250 Rate 250 Rate

Corn Insect Control with Monsanto Corn Insect Traits and Seed Treatments


40

ACCase InhibitorsAryloxyphenoxy Propionic Acids and Cyclohexanediones (Including Assure® II, Fusion®, Poast® and Select Max®)

Symptoms of damage from acetyl coA carboxylase inhibitors include chlorosis (yellowing) of newly formed leaves with possible reddening or purpling of older leaves. Tissues at the growing point turn brown and eventually decompose, a symptom

called deadheart. Sublethal doses result in pale white to yellow streaks between leaf veins.

ALS Inhibitors Imidazolinones, Sulfonylureas, and Triazolopyrimidines (Including Accent Gold®, Beacon®, Classic®, FirstRate®, Lightning®, Pursuit®, and Scepter®)

These herbicides alter the function of the acetolactate synthase (ALS) enzyme and affect root and shoot growth and development. Corn injury typically shows up as reduced root systems, often described as “bottle-brush” roots. Roots often grow flat or

parallel to the soil surface and may turn brown. Stems and midribs can purple, and the stem will be short and thick below the whorl. Mid– to late-season symptoms include short internodes, malformed leaves, poor root systems, and pinched ears.

Herbicides with sulfonylurea chemistry are labeled for use on both corn and soybeans. Products in this family may persist in the soil, particularly if soil pH is above 6.8 and post-application rainfall has been limited. Though they have the same general chemistry, different herbicides are used on corn and soybeans, and injury of corn may develop the

season following sulfonylurea herbicide application to soybean fields.

Most observed herbicide damage is due to misapplication, but hybrid and environment interactions will sometimes cause injury symptoms to appear. Herbicides used to control weeds in the previous crop must be taken into consideration, as some herbicide carryover may affect the following corn crop.

Various tankmixes of herbicides are widely used. Be alert to plant injury that can be caused by individual tankmix components or by an interaction involving two or more components in the tankmix itself.

Corn plants frequently outgrow the effects of herbicide injury and their final yields may not be noticeably lowered.

7Herbicide Injury Symptoms


Synthetic Auxins Benzoic Acids, Phenoxys, and Pyridine Carboxylic Acids (Including Banvel®, Butyrac®, Clarity®, and Crossbow®)

These herbicides, also known as plant growth regulators, are translocated to meristematic tissue and interfere with cell formation resulting in abnormal root and shoot

growth. Symptoms include twisted whorls or buggy-whipping where the leaves do not unfurl, abnormal brace roots, root proliferation, brittle stalks, and poor pollination. Growing conditions are a factor in damage expression.

Auxin Transport Inhibitors Semicarbazones (Including Distinct®and Status®)These herbicides are primarily active against broadleaf plants, but injury symptoms may occur in corn under certain conditions. Injury is similar to growth regulator herbicides.

Carotenoid Synthesis Inhibitors Isoxazolidinones(Including Command®)

Shallow planting or stress conditions that slow seedling metabolism can increase the potential for injury. Damage to corn seedlings the season following an application may occur, especially if soil pH is below 6.0. Affected plants are distinctly white

or bleached. Most corn plants recover and new leaves have normal color.

Cell Division InhibitorsAmides (Including Degree®, Dual II Magnum®, and Harness®)

Amides (also known as acetanilides, acetamides, or chloroacetamides) are meristematic growth inhibitors that are translocated to the shoot and leaves. These products can cause seedlings to leaf underground or trap

seedling leaves so they cannot unfurl, giving a ladder effect. Damage is more likely to take place with cool, wet weather occurring immediately before emergence.

EPSP Synthase Inhibitors Glycines (Including Roundup® agricultural herbicides and generic formulations of glyphosate)

These non-selective foliar-applied herbicides are translocated and interfere with amino

acid synthesis. If spray drift reaches corn, leaves wilt, turn brown, and die. Sublethal rates can cause phenoxy-like symptoms. Glyphosate applications that occur too late to corn with Roundup Ready® 2 Technology can result in poor kernel set.

Glutamine Synthase InhibitorsPhosphinic Acids (Including Ignite® and Liberty®)Inhibitors of glutamine synthase are nonspecific and will kill plants that have not been modified to express

42

resistance to them. Symptomology will range from light speckling on leaves and yellowing to plant death, depending on the degree and intensity of drift or spray contamination.

4-HPPD InhibitorsIsoxazoles and Triketones (Including Balance®, Balance® Pro, Callisto®, and Impact®)

Injury symptoms range from minor yellowing, through completely bleached plants, to

significant stand loss. Shallow planting or stress conditions that slow seedling metabolism can increase the potential for injury. New tissue development should not be affected and the effect of injury on yield potential will vary from field to field.

Microtubule Inhibitors Dinitroanilines (Including Prowl® and Treflan®)

Dinitroanilines function by inhibiting root and shoot growth. Injury can occur due to carryover from an application made the previous season. Seedling roots are pruned and clubbed. Stunting and purplish discoloration may occur above ground.

Symptoms may be confused with nematode damage.

PPO Inhibitors Diphenyl Ethers, Phenylphthalimides, Pyrimidines, and Triazolinones (Including Aim®, Authority®, FlexStar®, Reflex®, and Resource®)Herbicide application during hot, humid conditions or before a long period of cool weather can result in crop

injury. Drift injury can occur if application takes place under windy conditions. Symptoms range from leaf speckling to browning and death of entire leaves. If enough plant tissue is affected, the plant may wilt and die.

The season following application in soybeans, non-degraded herbicide residue can cause interveinal bleaching and discoloration of corn seedlings if post-application rainfall was unusually low.

Photosystem I Electron DiversionBipyridiliums (Including Gramoxone Inteon™)Drift of these non-selective contact herbicides may cause leaf spotting. Symptoms can be confused with disease; however, the dead leaf areas will not spread.

Photosystem II Inhibitors—mobile within plantTriazines and Ureas(Including atrazine, AAtrex®, Princep®, Sencor® and Lorox®)These chemical families inhibit photosynthesis, which leads to leaf yellowing, browning, and death, usually starting at the leaf margins and tip. New leaves may be symptom-free. Symptoms are more common on sandy soil where an excessive rate was applied. Unfavorable growing conditions may accentuate plant injury.

Photosystem II Inhibitors—nonmobile within plantBenzothiadiazoles and Nitriles (Including Basagran®and Buctril®) These are contact herbicides that are absorbed through the foliage. Leaf speckling after foliar application is a common injury symptom.


HERBICIDE MODES OF ACTION CLASS OF CHEMISTRY TRADEMARK OWNER

Acetyl CoA Carboxylase Inhibitors AryloxphenoxypropionatesAssure® II Fusilade® DXFusion®

Hoelon®

ACCase InhibitorACCase InhibitorACCase Inhibitor + ACCase Inhibitor

ACCase Inhibitor

AryloxyphenoxypropionateAryloxyphenoxypropionateAryloxyphenoxypropionate + AryloxyphenoxypropionateAryloxyphenoxypropionate

E.I. du Pont de Nemours & Co.SyngentaSyngenta

Bayer

Acetyl CoA Carboxylase Inhibitors CyclohexanedionesPoast®

Poast Plus®

Select®

Select MAX®

ACCase InhibitorACCase InhibitorACCase Inhibitor ACCase Inhibitor

CyclohexanedioneCyclohexanedioneCyclohexanedione Cyclohexanedione

BASFBASFValent USA CorporationValent USA Corporation

Acetolactate Synthase Inhibitors ImidazolinonesAuthority® AssistOptill™Lightning®

Pursuit®

Pursuit® PlusRaptor®

Scepter®

Squadron®

Steel®

ALS Inhibitor + PPO Inhibitor

ALS Inhibitor + PPO InhibitorALS Inhibitor + ALS InhibitorALS Inhibitor ALS Inhibitor + Microtubule InhibitorALS InhibitorALS InhibitorALS Inhibitor + Microtubule InhibitorALS Inhibitor + ALS Inhibitor + Microtubule Inhibitor

Imidazolinone + Triazolinone

Imidazolinone + PyrimidinedioneImidazolinone + ImidazolinoneImidazolinoneImidazolinone + DinitroanilineImidazolinone Imidazolinone Imidazolinone + Dinitroaniline Imidazolinone + Imidazolinone + Dinitroaniline

FMC Corporation

BASFBASFBASFBASFBASFBASFBASFBASF

Acetolactate Synthase Inhibitors SulfonylureasAccent®

Accent Gold®

Authority® XLBeacon®

Canopy®

Celebrity® Plus

Classic®

Exceed®

NorthStar®

Option®

Peak®

Permit®

Realm™ QResolve® Q Spirit®

Steadfast®

Steadfast® ATZ

Synchrony® XPValor® XLTYukon®

ALS Inhibitor ALS Inhibitor + ALS Inhibitor +

ALS Inhibitor + PPO InhibitorALS Inhibitor + AuxinALS Inhibitor ALS Inhibitor + PPO InhibitorALS Inhibitor + Auxin + Auxin Transport InhibitorALS InhibitorALS Inhibitor + ALS InhibitorALS InhibitorALS Inhibitor + AuxinALS InhibitorALS Inhibitor + 4-HPPD InhibitorALS Inhibitor + ALS InhibitorALS Inhibitor + ALS Inhibitor ALS Inhibitor + ALS InhibitorALS Inhibitor + ALS Inhibitor + PS II InhibitorALS Inhibitor + ALS InhibitorPPO Inhibitor + ALS InhibitorrALS Inhibitor + Auxin

SulfonylureaSulfonylurea + Sulfonylurea + Triazolopyrimidine + PyridineSulfonylurea + TriazolinoneSulfonylureaSulfonylurea + Triazine Sulfonylurea + Benzoic Acid + SemicarbazoneSulfonylureaSulfonylurea + SulfonylureaSulfonylurea + Benzoic AcidSulfonylureaSulfonylureaSulfonylureaSulfonylurea + TriketoneSulfonylurea + SulfonylureaSulfonylurea + SulfonylureaSulfonylurea + SulfonylureaSulfonylurea + Sulfonylurea + Triazine

Sulfonylurea + SulfonylureaPhenylphthalimide + SulfonylureaBenzoic Acid + Sulfonylurea

E.I. du Pont de Nemours & Co.E.I. du Pont de Nemours & Co.

FMC CorporationSyngentaE.I. du Pont de Nemours & Co.BASF

E.I. du Pont de Nemours & Co.SyngentaSyngentaBayerSyngentaNissan Chemical Industries, LtdE.I. du Pont de Nemours & Co.E.I. du Pont de Nemours & Co.SyngentaE.I. du Pont de Nemours & Co.E.I. du Pont de Nemours & Co.

E.I. du Pont de Nemours & Co.Valent USA CorporationNissan Chemical Industries, Ltd.

Herbicides that may be used or trigger symptomology in corn, grouped by mode of action and class of chemistry.

Herbicides shown in bold type contain two or more active ingredients, so they may appear in more than one section of the table.

44


Acetolactate Synthase Inhibitors TriazolopyrimidinesAccent Gold®

Authority™ FirstBroadstrike™

FirstRate®

Gangster®

Gauntlet®

Hornet®

Python®

SureStart™

TripleFLEX™ Herbicide

ALS Inhibitor + ALS Inhibitor + ALS Inhibitor + AuxinALS Inhibitor + PPO InhibitorALS InhibitorALS InhibitorALS Inhibitor + PPO Inhibitor

ALS Inhibitor + PPO InhibitorALS Inhibitor + AuxinALS InhibitorALS Inhibitor + Auxin + Cell Division InhibitorCell Division Inhibitor + Auxin + ALS Inhibitor

Pyridine + Sulfonylurea + Sulfonylurea + TriazolopyrimidineTriazolopyrimidine + TriazolinoneTriazolopyrimidineTriazolopyrimidine Triazolopyrimidine + PhenylphthalimideTriazolopyrimidineTriazolopyrimidine + TriazolinoneTriazolopyrimidine + PyridineTriazolopyrimidineTriazolopyrimidine + Pyridine + Amide + Pyridine + Triazolopyrimidine

E.I. du Pont de Nemours & Co.

FMC CorporationDow AgroSciences LLCDow AgroSciences LLCValent USA Corporation

FMC CorporationDow AgroSciences LLCDow AgroSciences LLCDow AgroSciences LLC

Monsanto Technology LLC

Synthetic Auxins Benzoic AcidsBanvel®Celebrity® Plus

Clarity®

Distinct®

Marksman®

NorthStar®

Status®

Yukon®

AuxinALS Inhibitor + Auxin + Auxin Transport InhibitorAuxinAuxin + Auxin Transport InhibitorAuxin + PS II InhibitorALS Inhibitor + AuxinAuxin + Auxin + Transport InhibitorALS Inhibitor + Auxin

Benzoic AcidSulfonylurea + Benzoic Acid + SemicarbazoneBenzoic AcidBenzoic Acid + SemicarbazoneBenzoic Acid + TriazineSulfonylurea + Benzoic AcidBenzoic Acid + SemicarbazoneBenzoic Acid + Sulfonylurea

BASFBASF

BASFBASFBASFSyngentaBASFNissan Chemical Industries, Ltd.

Synthetic Auxins Phenoxy Carboxylic Acids2,4-DButyrac®

Crossbow®

AuxinAuxin Auxin + Auxin

PhenoxyPhenoxyPhenoxy + Pyridine

Generic chemical nameAllbaugh, Inc.Dow AgroSciences LLC

Synthetic Auxins Pyridine Carboxylic AcidsAccent Gold®

Crossbow®

Hornet®

Stinger®

SureStart™

Tordon®

Transline®

TripleFLEX™

HerbicideWideMatch®

ALS Inhibitor + ALS Inhibitor + ALS Inhibitor + AuxinAuxin + Auxin ALS Inhibitor + AuxinAuxinALS Inhibitor + Auxin + Cell Division InhibitorAuxinAuxinCell Division Inhibitor + Auxin + ALS InhibitorAuxin + Auxin

Pyridine + Sulfonylurea + Sulfonylurea + TriazolopyrimidinePhenoxy + Pyridine Triazolopyrimidine + PyridinePyridineTriazolopyrimidine + Pyridine + AmidePyridinePyridineAmide + Pyridine + TriazolopyrimidinePyridine + Pyridine


Dow AgroSciences LLCDow AgroSciences LLC.Dow AgroSciences LLCDow AgroSciences LLC

Dow AgroSciences LLCDow AgroSciences LLCMonsanto Technology LLC

Dow AgroSciences LLC

Auxin Transport Inhibitors SemicarbazonesCelebrity® Plus

Distinct®

Status®

ALS Inhibitor + Auxin + Auxin Transport InhibitorAuxin + Auxin Transport InhibitorAuxin + Auxin + Transport Inhibitor

Sulfonylurea + Benzoic Acid + SemicarbazoneBenzoic Acid + SemicarbazoneBenzoic Acid + Semicarbazone

BASF

BASFBASF




Carotenoid Synthesis Inhibitors IsoxazolidinonesCommand®

Command® Xtra

Commence®

Carotenoid Synthesis InhibitorCarotenoid Synthesis Inhibitor + PPO InhibitorCarotenoid Synthesis Inhibitor + Micrutubule Inhibitor

IsoxazolidinoneIsoxazolidinone + Triazolinone

Isoxazolidinone + Triazolinone

FMC CorporationFMC Coporation

FMC Coporation

Cell Division Inhibitors AmidesAxiom® Define™

Degree®

Degree Xtra ®

Domain™

Dual II Magnum®

Guardsman Max®

Expert®

Halex™ GT

Harness®

Harness® XtraLexar®

Lumax®

Micro-Tech®

Outlook®

Radius™

SureStart™

TripleFLEX™

HerbicideVerdict™

Warrant™

Herbicide

Cell Division Inhibitor + PS II InhibitorCell Division InhibitorCell Division InhibitorCell Division Inhibitor + PS II InhibitorCell Division Inhibitor + PS II InhibitorCell Division Inhibitor Cell Division Inhibitor + PS II InhibitorCell Division Inhibitor + PS II Inhibitor + EPSPS InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + EPSPS InhibitorCell Division Inhibitor Cell Division Inhibitor + PS II InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II InhibitorCell Division InhibitorCell Division InhibitorCell Division Inhibitor + 4-HPPD InhibitorALS Inhibitor + Auxin + Cell Division InhibitorCell Division Inhibitor + Auxin + ALS InhibitorPPO Inhibitor + Cell Division InhibitorCell Division Inhibitor

Amide + TriazineAmideAmideAmide + TriazineAmide + TriazineAmideAmide + TriazineAmide + Triazine + Glycine

Amide + Triketone + Glycine

AmideAmide + TriazineAmide + Triketone + Triazine

Amide + Triketone + Triazine

AmideAmideAmide + Isoxazole

Triazolopyrimidine + Pyridine + AmideAmide + Pyridine + TriazolopyrimidinePyrimidinedione + ChloroacetamideAmide

BayerBayerMonsanto Technology LLCMonsanto Technology LLCBayerSyngentaBASFSyngenta

Syngenta

Monsanto Technology LLCMonsanto Technology LLCSyngenta

Syngenta

Monsanto Technology LLCBASFBayer

Dow AgroSciences LLC


BASFMonsanto Technology LLC

EPSP Synthase Inhibitors GlycinesExpert®

Flexstar® GTGlyphomax®

Halex™ GT

Roundup PowerMAX®

Roundup WeatherMAX®

Touchdown®

Cell Division Inhibitor + PS II Inhibitor + EPSPS InhibitorPPO Inhibitor + EPSPS InhibitorEPSPS InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + EPSPS InhibitorEPSPS Inhibitor

EPSPS Inhibitor

EPSPS Inhibitor

Glycine + Triazine

Diphenyl Ether + GlycineGlycineAmide + Isoxazole + Glycine

Glycine

Glycine

Glycine

Syngenta

SyngentaDow AgroSciences LLCSyngenta



Syngenta

Glutamine Synthase Inhibitors Phosphinic AcidsIgnite®

Liberty®

Liberty® ATZ

GS InhibitorGS InhibitorGS Inhibitor + PS II Inhibitor

Phosphinic AcidPhosphinic AcidPhosphinic Acid + Triazine

BayerBayerBayer


46


4-Hydroxyphenyl-Pyruvate-Dioxygenase Inhibitor Isoxazole

Balance®

Balance® FlexBalance® ProCorvus™

Laudis™

4-HPPD Inhibitor4-HPPD Inhibitor4-HPPD Inhibitor4-HPPD Inhibitor4-HPPD Inhibitor

Isoxazole IsoxazoleIsoxazoleIsoxazoleIsoxazole

BayerBayerBayerSyngentaBayer

Radius™ Cell Division Inhibitor + 4-HPPD Inhibitor

Amide + Isoxazole Bayer

4-Hydroxyphenyl-Pyruvate-Dioxygenase Inhibitor Triketones

Callisto®

Halex™ GT

Impact®

Lexar®

Lumax®

Realm™ Q

4-HPPD InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + EPSPS Inhibitor4-HPPD InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II InhibitorALS Inhibitor + 4-HPPD Inhibitor

TriketoneAmide + Triketone + Glycine

TriketoneTriketone

Amide + Triketone + Triazine

Sulfonylurea + Triketone

SygentaSygenta.

Amvac Chemical CorporationSyngenta

Sygenta


Microtubule Inhibitors DinitroanilinesCommence®

Pendimax®

Prowl®Prowl® H2OPursuit® PlusSonalan®

Squadron®

Steel®

Treflan®

trifluralin

Carotenoid Synthesis Inhibitor + Micrutubule InhibitorMicrutubule InhibitorMicrutubule InhibitorMicrutubule InhibitorALS Inhibitor + Micrutubule InhibitorMicrutubule InhibitorALS Inhibitor + Micrutubule InhibitorALS Inhibitor + ALS Inhibitor + Micrutubule InhibitorMicrutubule InhibitorMicrutubule Inhibitor

Isoxazolidinone + Dinitroaniline

DinitroanilineDinitroanilineDinitroanilineImidazolinone + DinitroanilineDinitroanilineImidazolinone + DinitroanilineImidazolinone + Imidazolinone + DinitroanilineDinitroanilineDinitroaniline

FMC Corporation

Dow AgroSciences LLCBASFBASFBASF Dow AgroSciences LLCBASF BASF

Dow AgroSciences LLCGeneric chemical name

Protoporphyrinogen Oxidase Inhibitors Diphenyl EthersBlazer® Cobra® FlexStar®

Flexstar® GTGoal®Phoenix™Reflex®

Storm®

Ultra Blazer®

PPO InhibitorPPO InhibitorPPO InhibitorPPO Inhibitor + EPSPS InhibitorPPO InhibitorPPO InhibitorPPO InhibitorPPO Inhibitor + PS II InhibitorPPO Inhibitor

Diphenyl EtherDiphenyl EtherDiphenyl EtherDiphenyl Ether + GlycineDiphenyl EtherDiphenyl EtherDiphenyl EtherDiphenyl Ether + BenzothiadiazoleDiphenyl Ether

United Phosphorus, Inc.Valent USA CorporationSyngentaSyngentaDow AgroSciences LLCValent USA CorporationSyngentaUnited Phosphorus, Inc.United Phosphorus, Inc.

Protoporphyrinogen Oxidase Inhibitors PhenylphthalimidesGangster®

Resource®

Valor® SXValor® XLT

ALS Inhibitor + PPO Inhibitor

PPO InhibitorPPO InhibitorALS Inhibitor + PPO Inhibitor

Triazolopyrimidine + PhenylphthalimidePhenylphthalimidePhenylphthalimidePhenylphthalimide + Sulfonylurea

Valent USA Corporation

Valent USA CorporationValent USA CorporationValent USA Corporation




Protoporphyrinogen Oxidase Inhibitors PyrimidinedionesOptill™Sharpen™

Verdict™

ALS Inhibitor + PPO InhibitorPPO InhibitorPPO Inhibitor + Cell Division Inhibitor

Imidazolinone + PyrimidinedionePyrimidinedionePyrimidinedione + Chloroacetamide

BASFBASFBASF

Protoporphyrinogen Oxidase Inhibitors TriazolinonesAim®

Authority®

Authority® AssistAuthority™ FirstAuthority® XLCommand® Xtra

Gauntlet®

PPO InhibitorPPO InhibitorALS Inhibitor + PPO InhibitorALS Inhibitor + PPO InhibitorALS Inhibitor + PPO InhibitorCarotenoid Synthesis Inhibitor + PPO InhibitorALS Inhibitor + PPO InhibitorrPPO Inhibitor

TriazolinoneTriazolinoneImidazolinone + TriazolinoneTriazolopyrimidine + TriazolinoneSulfonylurea + TriazolinoneIsoxazolidinone + Triazolinone

Triazolopyrimidine + TriazolinoneTriazolinone

FMC CorporationFMC CorporationFMC CorporationFMC CorporationFMC CorporationFMC Corporation

FMC Corporation

Photosystem I Electron Diversion Bipyridiliumsdiquat®

Reward®

Gramoxone Inteon™

PS I Inhibitor PS I InhibitorPS I Inhibitor

BipyridiliumBipyridiliumBipyridilium

Generic chemical nameSyngentaSyngenta

Photosystem II Inhibitors BenzothiadiazolesBasagran®

Laddok®

Storm®

PS II InhibitorPS II Inhibitor + PS II InhibitorPPO Inhibitor + PS II Inhibitor

BenzothiadiazoleBenzothiadiazole + TriazineDiphenyl Ether + Benzothiadiazole

BASFBASFUnited Phosphorus, Inc.

Photosystem II Inhibitors NitrilesBison®

Buctril®Moxy®

PS II InhibitorPS II InhibitorPS II Inhibitor

NitrileNitrileNitrile

Winfield Solutions, LLCBayerWinfield Solutions, LLC

Photosystem II Inhibitors TriazinesAatrex®

atrazineAxiom®

Canopy®

Degree Xtra®

Domain™Guardsman Max®

Harness® XtraLaddok®

Lexar®

Liberty® ATZ Lumax®

Marksman®

Princep®

Sencor®

Steadfast® ATZ

PS II InhibitorPS II InhibitorCell Division Inhibitor + PS II InhibitorALS Inhibitor + PS II InhibitorCell Division Inhibitor + PS II InhibitorCell Division Inhibitor + PS II InhibitorCell Division Inhibitor + PS II InhibitorCell Division Inhibitor + PS II InhibitorPS II Inhibitor + PS II InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II Inhibitor GS Inhibitor + PS II InhibitorCell Division Inhibitor + 4-HPPD Inhibitor + PS II InhibitorAuxin + PS II InhibitorPS II InhibitorPS II InhibitorALS Inhibitor + ALS Inhibitor + PS II Inhibitor

TriazineTriazineAmide + TriazinoneSulfonylurea + TriazineAmide + TriazineAmide + TriazineAmide + TriazineAmide + TriazineBenzothiadiazole + TriazineAmide + Isoxazole + Triazine

Phosphonic Acid + TriazineAmide + Isoxazole + Triazine

Benzoic Acid + TriazineTriazineTriazineSulfonylurea + Sulfonylurea + Triazine

SyngentaGeneric chemical nameBayerE.I. du Pont de Nemours & Co.Monsanto Technology LLCBayerBASFMonsanto Technology LLCBASFSyngenta

BayerSyngenta

BASFSyngentaBayerE.I. du Pont de Nemours & Co

Photosystem II Inhibitors UreasLorox® PS II Inhibitor Urea E.I. du Pont de Nemours & Co.


48

Herbicides by Active Ingredient and Mode of Action

HERBICIDE ACTIVE INGREDIENT MODE OF ACTION

2,4-D 2,4-D Auxin

AAtrex® Atrazine PS II Inhibitor

Accent® Nicosulfuron ALS Inhibitor

Accent Gold® Clopyralid + Flumetsulam + Nicosulfuron + Rimsulfuron

ALS Inhibitor + ALS Inhibitor + ALS Inhibitor + Auxin

Aim® Carfentrazone PPO Inhibitor

Assure® II Quizalofop ACCase Inhibitor

atrazine Atrazone PS II Inhibitor

Authority® Sulfentrazone PPO Inhibitor

Authority® Assist Imazethapyr + Sulfentrazone ALS Inhibitor + PPO Inhibitor

Authority™ First Cloransulam + Sulfentrazone ALS Inhibitor + PPO Inhibitor

Authority® XL Chlorimuron + Sulfentrazone ALS Inhibitor + PPO Inhibitor

Axiom® Flufenacet + Metribuzin Cell Division Inhibitor + PS II Inhibitor

Balance® Isoxaflutole 4-HPPD Inhibitor

Balance® Flexx Isoxaflutole 4-HPPD Inhibitor

Balance® Pro Isoxaflutole 4-HPPD Inhibitor

Banvel® Dicamba Auxin

Basagran® Bentazon PS II Inhibitor

Beacon® Primisulfuron ALS Inhibitor

Bison® Bromoxynil PS II Inhibitor

Blazer® Aciflourfen PPO Inhibitor

Broadstrike™ Flumetsulam ALS Inhibitor

Buctril® Bromoxynil PS II Inhibitor

Butyrac® 2,4-DB Auxin

Callisto® Mesotrione 4-HPPD Inhibitor

Canopy® Chlorimuron + Metribuzin ALS Inhibitor + PS II Inhibitor

Celebrity® Plus Dicamba + Diflufenzopyr + Nicosulfuron ALS Inhibitor + Auxin + Auxin Transport Inhibitor

Clarity® Dicamba Auxin

Classic® Chlorimuron ALS Inhibitor

Cobra® Lactofen PPO Inhibitor

Command® Clomazone Carotenoid Synthesis Inhibitor

Command® Xtra Clomazone + Sulfentrazone Carotenoid Synthesis Inhibitor + PPO Inhibitor

Commence® Clomazone + Trifluralin Carotenoid Synthesis Inhibitor + Microtubule Inhibitor

Corvus™ Isoxaflutole 4-HPPD Inhibitor

Crossbow® 2,4-D + Triclopyr Auxin + Auxin



Define™ Flufenacet Cell Division Inhibitor

Degree® Acetochlor Cell Division Inhibitor

Degree Xtra® Acetochlor + Atrazine Cell Division Inhibitor + PS II Inhibitor

diquat Diquat PS I Inhibitor

Distinct® Dicamba + Diflufenzopyr Auxin + Auxin Transport Inhibitor

Domain® Flufenacet + Metribuzin Cell Division Inhibitor + PS II Inhibitor

Dual II Magnum® Metolachlor Cell Division Inhibitor

Exceed® Primisulfuron + Prosulfuron ALS Inhibitor + ALS Inhibitor

Expert® Atrazine + Glyphosate + Metolachlor Cell Division Inhibitor + PS II Inhibitor + EPSPS Inhibitor

FirstRate® Cloransulam ALS Inhibitor

Flexstar® Fomesafen PPO Inhibitor

Fusilade® DX Fluazifop ACCase Inhibitor

Flexstar® GT Fomesafen + Glyphosate PPO Inhibitor + EPSPS Inhibitor

Fusion® Fenoxaprop + Fluazifop ACCase Inhibitor + ACCase Inhibitor

Gangster® Cloransulam + Flumioxazin ALS Inhibitor + PPO Inhibitor

Gauntlet® Cloransulam + Sulfentrazone ALS Inhibitor + PPO Inhibitor

Glyphomax® Glyphosate EPSPS Inhibitor

Goal® Oxyfluorfen PPO Inhibitor

Gramoxone Inteon™ Paraquat PS I Inhibitor

Guardsman Max® Atrazine + Dimethenamid Cell Division Inhibitor + PS II Inhibitor

Halex™ GT Glyphosate + Mesotrione + Metolachlor Cell Division Inhibitor + 4-HPPD Inhibitor + EPSPS Inhibitor

Harness® Acetochlor Cell Division Inhibitor

Harness® Xtra Acetochlor + Atrazine Cell Division Inhibitor + PS II Inhibitor

Hoelon® Diclofop ACCase Inhibitor

Hornet® Clopyralid + Flumetsulam ALS Inhibitor + Auxin

Ignite® Glufosinate GS Inhibitor

Impact® Topramezone 4-HPPD Inhibitor

Laddok Atrazine + Bentazon PS II Inhibitor + PS II Inhibitor

Laudis™ Tembotrione 4-HPPD Inhibitor

Lexar® Atrazine + Mesotrione + Metolachlor Cell Division Inhibitor + 4-HPPD Inhibitor + PS II Inhibitor

Liberty® Glufosinate GS Inhibitor

Liberty® ATZ Atrazine + Glufosinate GS Inhibitor + PS II Inhibitor

Lightning® Imazapyr + Imazethapyr ALS Inhibitor + ALS Inhibitor

Lorox® Linuron PS II Inhibitor

Herbicides by Active Ingredient and Mode of Action (cont.)

50



Lumax® Atrazine + Mesotrione + Metolachlor Cell Division Inhibitor + 4-HPPD Inhibitor + PS II Inhibitor

Marksman® Atrazine + Dicamba Auxin + PS II Inhibitor

Micro-Tech® Alochlor Cell Division Inhibitor

Moxy™ Bromoxynil PS II Inhibitor

NorthStar® Dicamba + Primisulfuron ALS Inhibitor + Auxin

Optill™ Imazethapyr + Saflufenacil ALS Inhibitor + PPO Inhibitor

Option® Foramsulfuron ALS Inhibitor

Outlook® Dimethenamid Cell Division Inhibitor

Peak® Prosulfuron ALS Inhibitor

Pendimax® Pendimethalin Microtubule Inhibitor

Permit® Halosulfuron ALS Inhibitor

Phoenix™ Lactofen PPO Inhibitor

Poast Plus® Sethoxydim ACCase Inhibitor

Poast® Sethoxydim ACCase Inhibitor

Princep® Simazine PS II Inhibitor

Prowl® Pendimethalin Microtubule Inhibitor

Prowl® H2O Pendimethalin Microtubule Inhibitor

Pursuit® Imazethapyr ALS Inhibitor

Pursuit® Plus Imazethapyr + Pendimethalin ALS Inhibitor + Mictrotubule Inhibitor

Python® Flumetsulam ALS Inhibitor

Radius™ Flufenacet + Isoxaflutole Cell Division Inhibitor + 4-HPPD Inhibitor

Raptor® Imazamox ALS Inhibitor

Realm™ Q Rimsulfuron + Mesotrione ALS Inhibitor + 4-HPPD Inhibitor

Reflex® Fomesafen PPO Inhibitor

Resolve® Q Rimsulfuron + Thifensulfuron ALS Inhibitor + ALS Inhibitor

Resource® Flumiclorac PPO Inhibitor

Reward® Diquat PS I Inhibitor

Roundup PowerMAX® Glyphosate EPSPS Inhibitor

Roundup WeatherMAX® Glyphosate EPSPS Inhibitor

Scepter® Imazaquin ALS Inhibitor

Select® Clethodim ACCase Inhibitor

Select MAX® Clethodim ACCase Inhibitor

Sencor® Metribuzin PS II Inhibitor

Sharpen™ Saflufenacil PPO Inhibitor



Sonalan® Ethalfluralin Microtubule Inhibitor

Spirit® Primisulfuron + Prosulfuron ALS Inhibitor + ALS Inhibitor

Squadron® Imazaquin + Pendimethalin ALS Inhibitor + Microtubule Inhibitor

Status® Dicamba + Diflufenzopyr Auxin + Auxin Transport Inhibitor

Steadfast® Nicosulfuron + Rimsulfuron ALS Inhibitor + ALS Inhibitor

Steadfast® ATZ Atrazine + Nicosulfuron + Rimsulfuron ALS Inhibitor + ALS Inhibitor + PS II Inhibitor

Steel® Imazaquin + Imazethapyr + Pendimethalin ALS Inhibitor + ALS Inhibitor + Microtubule Inhibitor

Stinger® Clopyralid Auxin

Storm® Bentazon PPO Inhibitor + PS II Inhibitor

SureStart™ Acetochlor + Clopyralid + Flumetsulam ALS Inhibitor + Auxin + Cell Division Inhibitor

SureStart™ Acetochlor + Clopyralid + Flumetsulam ALS Inhibitor +Auxin + Cell Division Inhibitor

Synchrony® XP Chlorimuron + Thifensulfuron ALS Inhibitor + ALS Inhibitor

Tordon® Picloram Auxin

Touchdown® Glyphosate EPSPS Inhibitor

Transline® Clopyralid Auxin

Treflan® Trifluralin Microtubule Inhibitor

trifluralin Trifluralin Microtubule Inhibitor

TripleFLEX™ Herbicide Acetochlor + Clopyralid + Flumetsulam Cell Division Inhibitor + Auxin + ALS Inhibitor

Ultra Blazer® Acifluorfen PPO Inhibitor

Valor® SX Flumioxazin PPO Inhibitor

Valor® XLT Flumioxazin + Chlorimuron PPO Inhibitor + ALS Inhibitor

Verdict™ Dimethenamid + Saflufenacil PPO Inhibitor + Cell Division Inhibitor

Warrant™ Herbicide Acetochlor Cell Division Inhibitor

WideMatch® Clorpyralid + Fluroxypyr Auxin + Auxin

Yukon® Dicamba + Halosulfuron ALS Inhibitor + Auxin


52

Boron (B)Boron deficiency is rare. Irregular white spots occur between leaf veins and may combine into white stripes with a raised waxy appearance. Bush-shaped plants often fail to produce a tassel or ear. Deficiency is favored by drought, high pH and sandy soil low in organic matter. Boron toxicity can cause yellow, dying leaf margins and tips.

Calcium (Ca)Symptoms of calcium deficiency are rare. Seedling leaf tips adhere to the next lower leaf, resulting in laddering effect and failure to unfurl normally. Deficiency is favored by very low pH (below 5.5) and high magnesium or potassium level.

Copper (Cu)Copper deficiency is rare. Young leaves yellow as they emerge from the whorl and may die at the tip and edges. Stalks are soft and flexible. Deficiency is favored by high organic matter soils.

Iron (Fe)Iron deficiency symptoms are rare. The upper leaves turn white between the veins, affecting the entire length. Symptoms are favored by high pH (alkaline) soil, cool weather, and wet, compacted soil.

Magnesium (Mg)Yellow-white streaking occurs between veins of lower leaves if magnesium is deficient. Eventually, margins and tips of older leaves become reddish-purple, then die. Deficiency is favored by low pH, sandy soil and high potassium levels.

9Nutrient Deficiency Symptoms

This section describes visual symptoms of moderate to severe nutrient deficiencies. These deficiencies are not always due to insufficient nutrient supplies in the soil. Symptoms are often induced by poor root development, root damage, unfavorable soil conditions (dry, water-logged, or compacted), or unfavorable weather. Nutrient availability is highly variable, strongly influenced by management decisions, and is only one component of soil productivity. Therefore, correction does not automatically require application of the suspected nutrient.

Mobile elements, like nitrogen, may become unavailable to plants because of leaching or gasification. Soil compaction, dry soil, soil where water has ponded, and inadequate rooting are examples of soil and plant conditions that may limit nutrient uptake. Specific nutrient deficiencies can be difficult to diagnose accurately. Soil and/or plant analysis may help identify and establish the cause of the symptoms. With these analyses be aware of possible nutrient interactions that may influence results.

Manganese (Mn)Manganese deficiency is rare. The area between leaf veins turns pale green-yellow. Stalks are thin and limber. Symptoms are favored by peat or muck soil, high pH and sandy soil high in organic matter.

Molybdenum (Mo)Molybdenum deficiency is rare. Young leaves sometimes twist, wilt and die along margins. Older leaves die at the tip, along margins and between veins. Deficiency is favored by low pH and strong soil weathering.

Nitrogen (N)Nitrogen-deficient plants are spindly, pale and stunted. Lower leaves develop a yellow- orange color in the shape of an inverted “V” beginning at the tip and following

the midvein. Leaves may begin to die (fire) at the tip. Symptoms advance up the plant to younger leaves. Ears are small and pinched at the tip. Symptoms are favored by cold, ponded, dry, or low organic matter soil, and incorporation of low-nitrogen residues.

Phosphorus (P)Leaves of young phosphorus- deficient plants are bluish-green and slightly narrowed, turning reddish-purple starting at the tips and along the edges. Leaf tips may die. If conditions for phosphorous uptake improve, newer

leaves may be symptom-free. Symptoms are seldom observed on knee-high and larger plants. Ears may be small and misshapen, twisted with one or more kernel rows missing on one side.

Potassium (K)Symptoms of potassium deficiency are seldom seen before plants are knee-high. Edges of lower leaves turn yellow and die (fire), starting at the tip. Leaves may break away. Plants are shortened. Ears are small and chaffy with poor tip-fill. Deficiency is favored by

wet or compacted soils, sandy or strongly weathered soil, and organic soil. Heavy potassium removal by previous crop can also favor deficiency.

Sulfur (S)Deficiency of sulfur causes stunted, slow-growing and yellow plants. Yellowing occurs between veins, especially of younger (upper) leaves. Older plants rarely show symptoms. Symptoms are favored by cold, wet soil, low pH, and low organic matter.

Zinc (Zn)Symptoms of zinc deficiency are rare beyond the seedling stage. Yellow to white bleached bands appear on the lower part of leaves while the midvein, margins and tip remain green. Newly affected leaves are sometimes described as “white buds.”

The deficiency is favored by high soil phosphorus, high pH, cool, wet soil and low organic matter – such as from exposed subsoil.


54

Index4-HPPD Inhibitors .. . . . . . . . . . . . . . . . . 42ACCase Inhibitors .................... 40Acetanilides . . . . ....................... 41ALS Inhibitors.... . . . . . . . . . . . . . . . . . . . ...40Amides .... . . . . . . . . . . . . . . . . . . . ..........41Anthracnose ..... . . . . . . . . . . . . . . . . . . . ...24Anthracnose Stalk Rot ... . . . . . . . .... 28Aphids ..... . . . . . . . . . . . . . . . . . . . . . . . ..... 31Armyworms ............................32Aryloxyphenoxy Propionic Acids .. . 40Aspergillus Ear and Kernel Rot ......29Auxin Transport Inhibitors . . . ........ 41Bacterial Leaf Blight ................. 24Bacterial Stalk Rot ........ . . . . . . . . . . . 28Bacterial Wilt .......................... 24Benzoic Acids .........................41Benzothiadiazoles .................... 42Billbug ... . . . . . . . . . . . . . . ................ 32Bipyridiliums .......................... 42Black Cutworm ..... . . . . .............. 35Blister Smut ....... . . . . . . . ............. 26Boil Smut ........ . . . . .................. 26Boron ... . . . . . . . . . . ... . . . ............... 52Calcium .................... . . . ......... 52Carotenoid Synthesis Inhibitors . . .. 41Cell Division Inhibitors ....... . . . . . . .. 41Cereal Leaf Beetle ....... . . . . . . . . . . .. 32Charcoal Rot .......................... 28Chinch Bug .................... . . . . ... 32Cladosporium Ear Rot . . . . . . . . . . .... 29Common Corn Rust ......... . . . . . ... 24Common Corn Smut ..... . . . . . ...... 26Common Stalk Borer ..... . . . . . ...... 32Copper ................................ 52Corn Borer ............ . . . . . . . . . . . . . .. 33Corn Earworm ....................... 33Corn Leaf Aphid ...... . . . . . . . ....... 31Corn Lethal Necrosis .... . . . . . . .... 27Corn Root Aphid .................... 31Corn Rootworm ..................... 34Corn Stunt Spiroplasma .... . . . . ...27Crazy Top ........... . . . . . . . . . . ........27Cutworm .............................. 35Cyclohexanediones .......... . . . . .... 40Dinitroanilines ................. . . ...... 42Diphenyl Ethers .............. . . ...... 42Diplodia Ear Rot ............ . . . ....... 30

Diplodia Stalk Rot ..... .... . . . . . ...... 28EPSP Synthase Inhibitors . . . ....... 41European Corn Borer .... . . . . ... . . . . 33 Eyespot ............... . . . . . . . . . ....... 26Fall Armyworm ...... . . . . . . . . ....... 32Flea Beetle ............ . . . . . . . . . ....... 35Fusarium Kernel or Ear Rot ... . . . ... 30Fusarium Stalk Rot ..... . . . . . . . . ..... 29Gibberella Ear Rot ....... . . . . . . . . . ... 30Gibberella Stalk Rot ......... . . . . . ... 29Glutamine Synthase Inhibitors ...... 41Glycines ................. . . . . . . . ....... 41Goss’s Wilt .............. . . . . . . . ....... 26Grape Colaspis ... . . . . . . . . . . . . ....... 35Grasshopper ........... . . . . . . . . ...... 35Gray Leaf Spot ....... . . . . .. . . . ....... 25Head Smut ............ . . . . . . . . ....... 26Helminthosporium Leaf Spot .. . . . .. 25High Plains Virus ........... . . . . . . .... 27Holcus Spot .... . . . . . . . . . . . . . . . ....... 25Imidazolinones ... . . . . . . . . . . . . . ....... 40Iron ................ . . . . ....... . . . ....... 52Isoxazoles ... . . . . . . . . . . . . . . . . . . ....... 42Isoxazolidinones ... . . . . . . . . . . . ....... 41Japanese Beetle ... . . . . . . . . . . . ....... 36Kernel Red Streak ....... . . . . . . . . .... 37Leaf Freckles and Wilt ...... . . . . . . . .. 26Leaf Miner ................... . . . ....... 36Lesser Cornstalk Borer ... . . . . . . .... 36Magnesium ... . . . . . . . . ...... . . . ....... 52Maize Chlorotic Dwarf Virus .. . . . ... 27 Maize Dwarf Mosaic Virus .. . . . . . ... 27Manganese .... . . . . . . . ...... . . . ....... 53Mexican Corn Rootworm . . . . ....... 34Microtubule Inhibitors ..... . . . ....... 42Molybdenum ........ . . . . . . . . . . ....... 53Nebraska Bacterial Wilt andLeaf Freckles ... . . . . . . . . . . .. . . . ....... 25Nitriles ........... . . . . . . . . . . . . . . ....... 42Nitrogen ........... . . . . . . . . . . . . ....... 53Northern Corn Leaf Blight ........... 26Northern Corn Rootworm .. . . ....... 34Northern Leaf Spot .. . . . . . . . . . ....... 25Penicillium Ear Rot .. . . . . . . . ... ....... 30Phaeosphaeria Leaf Spot .. . . . ...... 26Phenoxys . . . . . . . . ........... . . . ....... 41Phosphinic Acids .......... . . . ....... 41

Phosphorus ................. . . . ....... 53Photosystem I Electron Diversion .. 42Photosystem II Inhibitors - mobile .. 42Photosystem II Inhibitors - nonmobile .. 42Physoderma Brown Spot . . . . . ...... 26Picnic Beetle ................ . . . ....... 36Pinched Ear Syndrome ........... . .. 40 Potassium ................... . . . ....... 53PPO Inhibitors .............. . . . ....... 42Pyridine Carboxylic Acids .. . . . ..... 41 Pyrimidines . . . . . . . .................... 42Pythium Stalk Rot .. . . . .............. . 29Red Root Rot ............... . . . ....... 29Sap Beetle .. . . . . . . . ......... . . . ....... 36Scavenger Beetle ..................... 36Seed Corn Beetle .... . . . . . .... ....... 36Seed Corn Maggot .. . . . ............. 36Semicarbazones . . .... . . . . . . . ....... 41Slug ..................................... 36Sorghum Downy Mildew ... . . . ...... 28Southern Corn Leaf Blight .. . . . ..... 26Southern Corn Rootworm .. . . . . .... 34Southern Corn Rust .................. 26Southwestern Corn Borer ........... 33Spider Mite ... . . . . . . . . ................. 37Stewart’s Disease .. . . . . . ............. 24Stewart’s Wilt .. . . . . . . ................. 24 Stink Bug .... . . . . . . .................... 37Sulfonylureas . . . . . . . . ................. 40Sulfur .... . . . . . . . ........................ 53Synthetic Auxins . . . . ................. 41Thrips ................................... 37Triazines ................................ 42Triazolinones .......................... 42 Triazolopyrimidines ................... 40 Trichoderma Ear Rot ................. 30 Triketones .............................. 42 True Armyworm ....................... 32 Ureas ................................... 42 Webworm ... . . . . . . . ................... 37Western Bean Cutworm ............. 35Western Corn Rootworm .. . . . . . . ... 34Wheat Curl Mite ... . . . . . . . ............ 38White Grub .. . . . . . . .................... 38 Wireworm .............................. 38Zinc ..................................... 48

Monsanto Company is a member of Excellence Through Stewardship® (ETS). Monsanto products are commercialized in accordance with ETS Product Launch Stewardship Guidance, and in compliance with Monsanto’s Policy for Commercialization of Biotechnology-Derived Plant Products in Commodity Crops. This product has been approved for import into key export markets with functioning regulatory systems. Any crop or material produced from this product can only be exported to, or used, processed or sold in countries where all necessary regulatory approvals have been granted. It is a violation of national and international law to move material containing biotech traits across boundaries into nations where import is not permitted. Growers should talk to their grain handler or product purchaser to confirm their buying position for this product. Excellence Through Stewardship® is a registered trademark of Biotechnology Industry Organization.

B.t. products may not yet be registered in all states. Check with your Monsanto representative for the registration status in your state.

Individual results may vary, and performance may vary from location to location and from year to year. This result may not be an indicator of results you may obtain as local growing, soil and weather conditions may vary. Growers should evaluate data from multiple locations and years whenever possible.

ALWAYS READ AND FOLLOW PESTICIDE LABEL DIRECTIONS. Roundup Ready® crops contain genes that confer tolerance to glyphosate, the active ingredient in Roundup® brand agricultural herbicides. Roundup® brand agricultural herbicides will kill crops that are not tolerant to glyphosate. Degree®, Harness®, TripleFLEX™ Herbicide, and Warrant™ Herbicide are not registered in all states. Degree®, Harness®, TripleFLEX™ Herbicide, and Warrant™ Herbicide may be subject to use restrictions in some states. Degree Xtra®, Harness®, and Micro-Tech® are restricted use pesticides and are not registered in all states. The distribution, sale, or use of an unregistered pesticide is a violation of federal and/or state law and is strictly prohibited. Check with your local Monsanto dealer or representative for the product registration status in your state. Tank mixtures: The applicable labeling for each product must be in the possession of the user at the time of application. Follow applicable use instructions, including application rates, precautions and restrictions of each product used in the tank mixture. Monsanto has not tested all tank mix product formulations for compatibility or performance other than specifically listed by brand name. Always predetermine the compatibility of tank mixtures by mixing small proportional quantities in advance. Acceleron and Design®, Asgrow and the A Design® , Degree Xtra®, Degree®, Genuity and Design®, Genuity Icons, Genuity®, Growing Knowledge and Design®, Harness®, Micro-Tech®, Roundup PowerMAX®, Roundup Ready 2 Technology and Design®, Roundup Ready®, Roundup WeatherMAX®, Roundup®, SmartStax and Design®, SmartStax®, Technology Development by Monsanto and Design®, TripleFLEX™ Herbicide, VT Double PRO™, VT Triple PRO™, Warrant™Herbicide, YieldGard VT and Design®, YieldGard VT Triple®, DEKALB and Design®, Monsanto imagine® and Vine Design®, and When Performance Counts® are trademarks of Monsanto Technology LLC. Permi® and YUKON® is a registered trademark of, and used under license from, Nissan Chemical Industries, Ltd. Ignite®, LibertyLink® and the Water Droplet Design®, and Poncho® are registered trademarks of Bayer. Herculex® is a registered trademark of Dow AgroSciences LLC. Authority® is a trademark of FMC Corporation. Gangster® and Valor® are registered trademarks of Valent U.S.A. Corporation. Respect the Refuge and Corn Design® and Respect the Refuge® are registered trademarks of National Corn Growers Association. All other trademarks are the property of their respective owners. ©2011 Monsanto Company.