aggressive and difficult weed identification and...

Aggressive and Difficult

Weed Identification and

ControlChuck Schuster

Extension Educator

University of Maryland Extension

[email protected]

WEED ARE JUST PLANTS OUT OF PLACE

Weeds In one Place => Desirable Plants in another

Vigorous growth Leads to rapid reproduction and

allows them to out-compete desirable plants

Start with Proper Identification

Assess the Site

Where is it?

Urban/Rural

Public/Private

Commercial/Industrial

Type of Site

Wooded/open

Ornamental

Wetland/Creek side

Agricultural

Adjacent areas/Borders

Limitations

Herbicide Limitations

Vineyard, Vegetables, Residential, Etc.

Drift /Volatizing

Neighbor Relations

Adjacent Vegetation Concerns

Assess The Site

Existing Growth/Cover

Species I.D.

Desirable Species

Undesirable Species

Endangered Species

Stage of Growth

Time of Year

Weed Population Density

Edge Effect

Site History

Type of use

Recent Change?

Prior Weed Control

Treatments

Herbicide, Mowing,

Plow/Disc

Fertility

Healthier cover=Less weeds

Assess The Site

Terrain

Flat / Cliff /Slopes/Ravines

Accessibility

Overgrown?

Flooding/Wet/Time of Year

People/Equipment Access

Erosion Control /Creek/Pond/Springs, etc. ? Water Quality Issues

Size

Will you be able to maintain areas?

Type of equipment needed/available

Time available for Maintenance

Right of Way Vegetation Control

In general apply herbicides to the smallest

area possible.

Avoid having large killed areas with no

vegetation as this leads to potential

erosion.

When possible use selective products to

allow low growing vegetation to continue to

exist.

7


Ground applications often use volumes

ranging from 100-500 gpa. Research has

shown good results with volumes as low as

30- 60 gpa if uniform coverage can be

obtained.

8


Note: Drift control agents such as Nalcotrol

or Polycontrol at labeled rates greatly

reduce risk of off Right-of-Way damage.

Use controlled size droplets to reduce risk

off of the Right-of-Way damage wherever

practical.

9

Guard Rails

Weed control treatments under and in front of the

guide rails usually involve chemical and/or

manual methods.

Guide rails can be treated with a variety of

techniques, such as a handgun, short boom with

nozzles spraying each side of the guide rail, flood

nozzles, or off-center nozzles treating in front of

and under the guide rail.

10

Cultural Control

Enhances Growth of Desirable

Ground Cover/Mulch

Choose cover that allows selective control

Vegetation Competition

Plant close together

Prevent Contamination

Clean Seed

Neighbors also control

Reduce Disturbance

Nature fills a gap

Fertilization/Soil ph

Canada Thistle

Cirsium arvense

Foliar treatment in spring with

follow up in fall or as needed

Transline/ Stinger (clopyralid) the

best

Establish grass cover

Multi year treatment

Exceeding Label Rates May Burn the Top Down, Look at the Depth of the Roots.

Ailanthus

Tree of Heaven

Ailanthus altissima

DO NOT CUT WITHOUT TREATING!

Basel Bark Treatment

Garlon 4/BaselOil

Pathfinder II

Cut Stump

Small trees and follow up with Foliar Escort

Bradford/Callery PearPyrus calleryana

Prevention

Cut Stump

Basel Treatment

Foliar

Krenite-?

Garlon 4

Mimosa TreeAlbiziz julibrissin

Empress TreePaulownia tomentosa

Multi Flora Rose

Rosa multiflora

Woody Perennial

Foliar

Escort

Dicamba/2,4-D

Glyphosate

Basel Bark Garlon

Cut Stump

Privet, Autumn OliveFoliar most

effective

Basel treatment can work well access is an issue

WineberryRubus phoenicolasius

PhragmitesPhragmites australis

Imazapyr /Habitat in summer

Glyphosate when in head - late Summer

Japanese StiltgrassMicrostegium vimineum

Pre-emergent herbicide ? Barricade

Stop Seed Production !

Hand pull

Mowing ineffective

Foliar Glyphosate or Grass herbicide in summer provides good control

Multi year treatments to reduce seed stock

Wavy Leaf Basket Grass

Oplismenus hirtellus subsp undulatifolius

Seeds on Boots

Populations are relatively small and can be

eradicated through hand removal or by treatment with a

two percent solution of glyphosate.

BAMBOO

BambooVery Tough to

control

Treatment with grass herbicide

Fall treatment with Glyphosate

Backhoe

Barrier of steel or plastic

Vines

Woody Vines

Oriental Bittersweet

Porcelain Berry

Vines

Japanese Honeysuckle

Japanese Hops

English Ivy

Foliar

Glyphosate

Garlon 3A

Basel Bark

Cut Stump

Cut out of trees to avoid damage

Mile A Minute

Persicaria perfoliata (Polygonum perfoliatum L.)

Annual

Foliar treat with broadleaf herbicide

Timing can be everything

Pre- emergent ? Some work, nothing really labeled.

Germinates throughout season

Multiple treats per year

Surfactant is VERY important!

Kudzu

Pueraria montana var. lobata

Perennial

Treatment with

Stinger/ Transline Foliar Minimizes damage to trees

Garlon /Dicamba/2,4-D Foliar

Garlon 4 Basel treatment

Glyphosate Foliar

Cut Vines off trees and then treat

Oriental Bittersweet

Celastrus orbiculatus

Porcelain BerryAmpelopsis Brevipedunculata

Beltway greenery

Mistaken for native grape

Large vines

Cut stump possible

Japanese KnotweedPolygonum cuspidatum

Perennial

Foliar Glyphosate

Foliar Arsenal

Treat July through frost

minimize rootstock movement

Multi year treatments

Purple Loosestrife

Perennial

Bio Control in works

Foliar spray with

aquatic Glyphosate

or habitat

Permits needed to

spray in wetlands

Garlic MustardAlliaria petiolata

Biannual

Stop Seed Production

Hand Pull

Treat foliar with Glyphosate or broadleaf herbicide

Multiyear control needed

WEED CONTROL ROUGH GUIDEThe Difference between impossible and possible control

STOP! Don’t Mow! Look at options first!

Better cover/stand=Better weed control

Prevention, start control before problem spreads

Disturb soil/cover as little as possible

Target difficult weeds first

Scout – Early detection/prevention

Leave time to control before doing a planting

What Limits The Pesticide

Application?

Equipment

Operator/Applicator Knowledge

Appropriate Products

Water Quality

Keeping the Product on the Plant

Water Quality and Herbicides

Water is the primary carrier for

herbicide applications

Spray solutions commonly contain

95% or more water

Interaction is determined by water

chemistry and herbicide chemistry

Water Chemistry

Water pH, hardness, alkalinity, and

turbidity can affect herbicide efficacy.

Water pH is the concentration of H+ ions

in the water.

Hard water is caused by high levels of

calcium, magnesium, sodium, or iron.

Water Chemistry (cont.)

Hardness is expressed as an equivalent of calcium carbonate in

water analysis tests

Turbidity is caused by suspended solids, soils, or organic matter

Alkalinity refers to carbonate and bicarbonate levels in water

Herbicide Chemistry (cont.)

The solubility of sulfonylurea herbicides (Envoke, Sandea) increases with

higher pH

The amount of dissociation depends on the pH of the water

Dissociated herbicide molecules have a negative charge

Herbicides with high Koc values are sensitive to turbid water

Koc is the organic carbon sorption coefficient, Koc is a measure of the

tendency of a chemical to bind to soils. Koc values can vary substantially,

depending on soil type, soil pH, the acid-base properties of the pesticide and

the type of organic matter in the soil.

Turbidity

The dirt and color you see in the water

They can easily deactivate herbicides with Koc values

Clean water is very important for these herbicides

Herbicides with low Koc values are not affected

pH of Natural Water Sources

If the pH of your spray water is higher than 7.5, it is alkaline enough to affect some pesticides.

A pH of 7.5-8.5 is common in many areas of the U.S. and in many surface and ground water sources in

Maryland.

There have been reports that 5% of the natural water supplies in the U.S. have a pH higher than 9.0.

Hard water contains more dissolved calcium and

magnesium.

Potomac water tends to be hard (typically averaging about

120–130 milligrams per liter).

Patuxent water is soft (typically averaging about 60–65

milligrams per liter).

pH of the water from the Patuxent River is 7.5 with a

range of 7.2-7.8

pH of water from the Potomac River is 7.5 with a range of

7.2-7.7

TRADE NAME COMMON NAME pH HYDROLYSIS RATE 50%

HYDROLYZED INDylox trichlorfon 8.0 6.3 minutes

7.0 6.4 hours

6.0 3.7 days

Guthion azinphos-methyl 9.0 12 hours

7.0 20 days

5.0 17.3 days

Carzol formetanate 9.0 3 hours

7.0 14 hours

5.0 17.3 days

Imidian -- 8.3 less than 4 hours

7.0 less than 12 hours

4.5 13 days

Dimecron phosphamidon 10.0 30 hours

7.0 13.5 days

4.0 74 days

Sevin carbaryl 9.0 24 hours

8.0 2-3 days

7.0 24-30 days

6.0 100-150 days

Gardona tetrachlorvinphos 10.5 80 hours

7.0 44 days

3.0 54 days

Phosdrin mevinphos 11.0 1.4 hours

7.0 35 days

TRADE NAME COMMON NAME pH HYDROLYSIS RATE 50%

HYDROLYZED IN

DiSyston disulfoton 9.0 7.2 hours

5.0 60 hours

-- EPN 10.0 8.2 hours

6.0 more than 1 year

-- Parathion 11.0 170 minutes

10.0 29 hours

7.0 120 days

5.0 690 days

-- TEPP 10.0 21 minutes

9.0 3.5 hours

6.0 6.8 hours

Lannate methomyl 9.1 Loses 5.0% of its effectiveness in 6 hours at a rate

of 8 oz. per 100 gal. water. Stable in slightly acid

solutions.

-- malathion above 7.0

below 3.0

Hydrolyzes rapidly.

Dibrom naled above 7.0 Hydrolyzes 90-100% in 48 hours.

DeFend, Cygon dimethoate between 4.0 and 7.0 Stability is at maximum. Unstable in alkaline

media.

Benlate benomyl above 7.0 Less soluble.

What Does Your Water

Source Do To Your Mix?

Well Water can have very high levels of

hardness, well above 800 in Central Maryland.

Water from streams and ponds can vary greatly

depending on water sources, what is happening

upstream and size of water reservoir.

Glyphosate Hardness higher than 350 mg/L can affect low rates and over 700mg/L can

affect high rates.

Glyphosate has a high Koc and is greatly affected by turbidity.

Effects can be reduced by-

Using higher rates

Adding ammonium sulfate to the spray solution

Using the spray immediately after mixing

Reducing carrier volume

2,4-D Amine

Water hardness levels of above 600 mg/L will likely cause interference

Alkalinity above 500 mg/L can reduce effectiveness

Consider alternate formulations or water sources

Clethodim, Sethoxydim, others

These grass herbicides are weak acids

Have low Koc values so they aren’t affected by turbidity

At pH values below 6 they are not affected by hard water

Higher pH allows dissociation and cation formation

Koc Values of Herbicides Commonly

used

2,4-D, Ametryn, Asulam, Atrazine, Dicamba, Diuron, Halosulfuron,

Hexazinone, Metribuzin, Sethoxydim, Trifloxysulfuron- low

Fluazifop- moderate- Can be a Problem

Glyphosate, Pendimethalin- high- Problems

Paraquat- very high- Problems Remember that KOC is the organic carbon sorption coefficient

Water source and create herbicide efficacy issues.

How to Adjust pH of Water- What to Add

• Spray-Aide (Miller)

• 6-8 oz./100 gallons

• $40/gallon

• Costs $2.50 per 100 gallons at 8 oz. rate

How to Adjust pH of Water- What to Add

• Nutrient Buffer Spray

• Utilizes nutrients to change water quality

• Available in several different analysises.

• Can contain trace minerals.

• Costs vary greatly.

Questions?

Miscanthus / Eulalia

Miscanthus sinensis

Common Dissolved Materials

Below are the 6 most common ions

found in water

Other ions can also have an effect

Anions (- charge)

Sulfate

Chloride

Bicarbonate

Cations (+ charge)

Calcium

Magnesium

Sodium

Total Dissolved Solids and Electrical

Conductivity

TDS is total dissolved solids

The sum of all the minerals dissolved in a water sample is the TDS

The higher the TDS, the more electrical current water can conduct (why)

EC is electrical conductivity

EC is used as a simple method to test for TDS

Herbicide Chemistry

Weak acids-compounds that release some H+ ions when dissolved in water

Many herbicides are weak acids: glyphosate, paraquat, sethoxydim

Weak acid herbicides partially dissociate in water

For most herbicides, the portion that does not dissociate is more easily absorbed by

plant leaves

Japanese Honeysuckle

Lonicera japonica

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