insects & diseases of vegetables combo - uga...

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Vegetable Diseases & Management Options

Abiotic Diseases

Cold Damage

Excess or Deficient Nutrients

pH

Lightning

Lack of Pollination

Moisture Stress

Tomato

Blossom End Rot

Calcium deficiency

Irregular watering

Vegetable Nutrition Problems

Mg- low pH, older leaves

Mn – high pH

K – cold soil, purpling

B – high pH, High Ca, dry weather, turnips

Mo – not common

Ca – low pH, lack of Ca, irregular watering

Plant Diseases are caused by…

1. Fungi - 80%2. Bacteria - 10%3. Nematodes - 5%4. Viruses - 5%5. Phytoplasmas

(Aster yellows)

Aster yellows on Carrots – malformed shoot growth – proliferation of tissue

Signs & Symptoms

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Preventative Management Strategies

1. Site selection

2. Crop rotation

3. Plant disease free seeds & transplants

4. Plant disease resistant varieties

5. Planting date management

6. Proper spacing & watering

7. Use a mulch layer

8. Proper fertilization

9. Maintain a weed-free garden

10. Avoid use of tobacco products

11. Sanitation

12. Pesticides

Vegetable Disease Control

1. Site Selection Well drained soil – excessive soil moisture causes root

and crown diseases (soil-borne diseases)

Full Sunlight – speeds drying of foliage – reduces most foliage diseases

Phytophthora diseases – pepper,

tomato, melon, squash, pumpkin,

eggplant, cucumber, & carrot

Pythium infection on beans – hot

temperatures & heavy rainfall

Sclerotinia sclerotiorum on beans – cool temperatures

Soilborne pathogens

Pythium spp. Phytophthora spp. Sclerotinia spp. – white mold Rhizoctonia solani – wirestem Sclerotium rolfsii – southern blight Macrophomina phaseolina – charcoal

rot Erwinia carotovora – bacteria Nematodes – various

Water molds


2. Crop Rotation – do not plant the same FAMILY of vegetable in same area year after year

Alliaceae Brassicaceae Cucurbitaceae Fabaceae Solanaceae

ChivesGarlicLeeksOnions

BroccoliBrussel sproutsCabbage CauliflowerCollardsLettuceMustard RadishRutabagaSpinachTurnip

CantaloupeCucumbersHoneydew melonsPumpkinsSquashWatermelon

All beanEnglish peasSouthern peas

EggplantTomatoesPeppersPotatoes

Asteraceae Poaceae Malvaceae Chenopodiaceae Apiaceae

Lettuce Corn Okra Spinach Carrot

Grow the same plants or closely related plants in the same soil only once every 3 to 5 years!!!


Rhizoctonia blightSouthern blight on carrot

Belly rot of cucumber

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Buckeye rot on tomato – Phytophthora spp.

Southern blight on tomato

(Sclerotium rolfsii)

Early symptoms – water-soaked lesions on crown & lower stem

Girdle the entire crown

Wilting & quick collapse of foliage


3. Plant Disease Free Seed and TransplantsDo not save seeds from year to year – many plant diseases are SEED-BORNE

Snap bean – halo blight, common blight, anthracnose Tomato – bacterial spot


4. Plant Resistant Varieties Most efficient way to manage disease

(PREVENTION) Example: TOMATOES:

“VFN” – resistance to Verticillium wilt (not common in GA), Fusarium wilt, and nematodes,

TSW – tomato spotted wilt, TMV – tobacco mosaic virus, ASC – Alternaria stem canker, PM – powdery mildew...

Good links: http://www.utextension.utk.edu/publications/spfiles/SP277-K.pdf; http://muextension.missouri.edu/explorepdf/agguides/hort/G06202.pdf

Fusarium wilt – general wilting/yellowing of plant

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Ralstonia solanacearum on tomato – Southern bacterial wilt


5. Planting Date Management Following the recommended planting dates

for a particular vegetable http://pubs.caes.uga.edu/caespubs/pubs/P

DF/B577.pdf Example: OKRA

Planted when soil temperatures are warm – good germination and growth

Planted when soil temperatures are cool – increase incidence of soil-borne diseases (sore shin & damping off)

Rhizoctonia

Vegetable Disease Control6. Proper spacing & watering

Spacing – allows growth & air circulation Extended periods of wet foliage – ideal for disease

development Crowded plants – take longer to dry Limit effectiveness of crop protectants – can not

penetrate the dense foliage Staking – tomatoes, beans, cucumbers

Watering – Avoid excessive soil moisture Over-watering – enhances seed decay, damping-off,

root & crown diseases Avoid splashing plants with soil & avoid overhead

watering (wetting the foliage) If drip irrigation is not practical, irrigate in the morning to

promote complete drying and avoid wetting foliage

DON’T WORK IN THE GARDEN WHEN PLANTS & SOIL ARE WET!


Bacterial spot on Tomato

Downy mildew of Cabbage –favored by moist conditions & water-splashing

Black rot of Cabbage –

black veins in yellow lesions characteristic for this disease

Powdery mildew on squash

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Squash

Powdery Mildew Downy Mildew

Alternaria leaf spot on ONION

= Alternaria leaf spot

Alternariablight on tomato

Choanephora fruit rot on SQUASH – whisker-like blossom end rot –due to excessive moisture


7. Use a mulch layer Straw, bark, shredded paper or plastic Prevent soil from touching plants & prevent fruit

from touching bare ground Helps prevent rots on mature fruit Conserves moisture & reduces weed infestations

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8. Proper Fertilization Avoid excessive amounts of nitrate nitrogen –

encourage root diseases Use Ammonium forms instead

9. Weed Free Garden Weeds – reservoirs for VIRUSES Weeds decrease air circulation & increase moisture

10. Avoid Tobacco use when working in garden –Tobacco Mosaic Virus (TMV) – tomatoes & peppers

Seedborne

Insects

Tobacco

VIRUS SYMPTOMS ON VARIOUS VEGES

VIRUS SYMPTOMS ON VARIOUS VEGES

TSWV

Cucumber Mosaic Virus

Spread by insects & mechanical means (tools) NO Chemical Control for Viruses Management of the Vector

TSWV on pepper

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Nematode Management:

Microscopic soil-inhabiting roundworms

Feed on roots Causing decay and/or

galling; stunting; wilting Most damaging in GA – Root-

knot nematode Reniform & sting – serious

problems also Root knot nematode damage to potato

Sting nematode damage to corn

Root knot nematode damage to watermelon


Soil solarization – reduces # of nematodes Till garden Cover area with clear plastic

tarp for 6 to 8 weeks Increase in temperature kills

nematodes in upper 3 to 4 inches of soil

When – June through August Rotations of non-susceptible crops (such as grass) –reduce populations

Resistant varieties of veggies Organic Amendment –

Nem-A-Cide – contains chitin (Hi-Yield product)

http://www.floridagardener.com/critters/bedbed.htm


Nematode management using MARIGOLDS Broadcast in early spring Left there all summer French dwarf marigolds – best

variety Acts as a Trap crop

Marigolds – source of spider mites

11. Sanitation Remove & destroy plant material after

harvest Plow soil to break down small roots & debris Remove & discard/destroy diseased plants

12. Pesticides Home gardeners have few pesticides Use as a last resort Read & follow label carefully

Vegetable Disease ControlInsects of Vegetables

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Insect Control in Vegetables

Five Basic Steps

1. Prevention

2. Early Detection

3. Correct Id of Pest and Beneficial Insects

4. Proper Selection of ControlInsecticides normally not used preventatively.

5. Proper Application

Corn Earworm (Tomato Fruitworm)

1 ¾ in. long Light green to pink to

brown or nearly black Alternating light and

dark stripes running the length of the body

Chews holes in pods or fruit of several vegetables, leaves of corn and tomatoes.

Aphids

Pale green to black 1/8 in long soft bodied insects, with tail pipes.

Mostly found feeding on new growth.

Piercing/sucking

Greatest concern is virus transmission.

Spider Mites

Tiny 8 legged pests that are often found underneath the leaf

Piercing/sucking mouthparts

Leaves appear stippled or bronzed above

Love it hot and dry

Fine webbing may be produced under heavy infestation

Stink Bugs

5/8 in long, bright green with narrow head

Fowl odor when crushed

Piercing/Sucking Toxic Saliva Brown spots on

beans/peas, whitish spots on tomato.

Flea Beetles

1/16 to 1/8 inch long shiny black or striped

Jump when disturbed

Very destructive, often in large numbers

Chewing Mouthparts

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Insect Pests of Specific Crops

Beans and Peas

Bean Leaf Beetle ¼ in long Reddish orange,

black band around outer margin with 3-4 spots where wings meet

Chewing Round holes in leaves

and stems

Beans and Peas

Cowpea Curculio

Black, hump-backed, hard-shelled beetles, ¼ in long, long slender snout

Wart like strings on pod surface eggs deposited inside of pod, larvae feed on peas/beans

Must be controlled during flower stage.

Beans and Peas

Mexican Bean Beetle

Coppery brown rounded beetles, ¼ in long, 16 black spots

Adults and larvae chewing mouth parts

Beans and Peas

European Corn Borer

Larvae 1 in. long flesh-colored with rows of small dark-brown spots. Dark brown head.

Bore into stems and pods which may cause breakage

Beans and Peas

Lesser Cornstalk Borer

¾ in. long slender, bluish-green, with brown horizontal stripes

Wilting of plants with girdling or boring into lower portion of stems.

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Beans and Peas

Thrips

Slender yellow or brown insects 1/25 in. long

Rasping mouthparts

Distorts flowers, white blotches on leaves

Beans and Peas

Whiteflies Very small winged

insect resembling a moth

Sucking mouthparts Fly out in a cloud

when disturbed Leaf color loss and

drop Sooty mold

Cucumbers, Melons, Squash & Pumpkins Cucumber Beetles

¼ in. long

Chewing mouthparts

Spotted CB – 12 black spots - Holes in leaves, flowers, bacterial wilt

Striped CB – 3 vertical stripes, holes in leaves, stems and fruit.

Cucumbers, Melons, Squash & Pumpkins Leafminers

Adult is a small fly

Larval stage (maggot) feeds on the tissue between the leaf layers weakening the leaves.

Treatment is not practical.

Cucumbers, Melons, Squash & Pumpkins Pickleworm Greenish to coppery

¾ in caterpillar with dark spots when young

Burrows into buds, flowers, vines and fruit pushing out green excrement. Fruit rots.

Cucumbers, Melons, Squash & Pumpkins Squash Bug Adult is a dingy gray-

black and nearly an inch long.

Nymphs are lime green with reddish heads.

Eggs are a bright copper color.

Adults and Nymphs sucking mouthparts, spotty loss of color, severely damaged leaves become crisp and die.

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Cucumbers, Melons, Squash & Pumpkins

Squash Vine Borer

Thick, white, wrinkled, Brown-headed caterpillars up to 1 in.

Yellowish brown frass

Usually attack vines at soil-line, vine usually wilt, rot then die.

Fruit is occasionally attacked in late season.

Cabbage, Collards, Broccoli, & Turnips

Cabbage Maggot

Yellowish white legless larvae, blunt rear, pointed at front

Maggot feeds on roots and stems near the soil line.

Wilting and death of seedlings.


Cabbage Looper

Pale green, smooth skinned caterpillars up to 1 ¼ in long

Loop as they move.

Chewing mouthparts.

Large holes in leaves.


Imported Cabbageworm

Larvae velvety green with a narrow orange stripe down the middle of the back and broken yellow stripes on sides 1 ¼ in. long.

Chew holes in leaves usually in the center of the plant.


Harlequin Bug

Shiny red and black, shield shaped 3/8 in. long

Sucking mouthparts.

Leaves develop yellow spots, brown the die.

Sweet Corn

• European Corn Borer

• Larvae 1 in. long flesh-colored with rows of small dark-brown spots. Dark brown head.

• Feeds in tassels and young leaves in a whorl, tunneling to stalk and ears.

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Sweet Corn

Fall Armyworm

Light green to black, striped, black head with inverted white y

Similar damage to corn earworm but will chew through husk to eat kernels.

Tomatoes, Eggplants, & Peppers

• European Corn Borer (Peppers only)

• Larvae 1 in. long flesh-colored with rows of small dark-brown spots. Dark brown head.

• Bore into stems which may cause breakage. May bore into fruit causing fruit drop.


Blister Beetle

Soft slender beetles 1-½ to 1 ¾ in long. Black or gray with yellow or gray stripes on wing covers

Chewing mouthparts.

Loss of leaves may result in sun scald.


Cutworms

Plump, smooth skinned, greasy-looking caterpillars up to an inch long

Often curled up at the base of the plant.

Young plants cut down at ground level. Dr. Dan Brown UGA


Tomato Hornworm Large green

caterpillar up to 3-4 in. long, white bars on sides

Long slender horn on posterior.

May defoliate plant and cause sun scald on fruit.

Parasitized by Braconid wasp


• Whiteflies• Very small winged

insect resembling a moth

• Sucking mouthparts• Fly out in a cloud

when disturbed• Leaf color loss and

drop• Sooty mold

insects & diseases of vegetables combo - uga...

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