aggressive and difficult weed identification and...
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Aggressive and Difficult
Weed Identification and
ControlChuck Schuster
Extension Educator
University of Maryland Extension
cfs@umd.edu
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
Right of Way Vegetation Control
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
Right of Way Vegetation Control
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
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
Japanese Honeysuckle
Lonicera japonica
Are you ready to control invasive weeds?
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