Using Herbicides Safely Using Herbicides Safely Around Woody PlantsAround Woody Plants
Off-site Movement of Herbicides
2013 Washington State Weed ConferenceBy: Paula Dinius, Urban Horticulturist
WSU Chelan County Extension
Fate of Herbicides after ApplicationFate of Herbicides after Application
Image source: http://pubs.usgs.gov/fs/2006/3028/pdf/fs2006-3028.pdf
Using Herbicides Around Using Herbicides Around Trees & ShrubsTrees & Shrubs
Mechanisms of Off-site Herbicide Movement Symptoms of Herbicide InjuryCase Studies
Using Herbicides Around Using Herbicides Around Trees & ShrubsTrees & Shrubs
Plant injury is usually caused by not following label directions.◦Using around sensitive plants◦Improper rate or method of application◦Spraying during adverse weather conditions◦Over/under irrigation
Using Herbicides Around Using Herbicides Around Trees &ShrubsTrees &Shrubs
Off-site movement is when any herbicide misses or moves from the intended treatment area.
Mechanisms of Off-Site MovementMechanisms of Off-Site Movement
Movement via air ◦Volatilization - vapor◦Drift – droplet and granule dust
Movement via soil water◦Leaching◦Run-off
Off-site Movement ~ VolatilizationOff-site Movement ~ Volatilization
High temperatures + low humidity = gas (vapor)
Fumes travel for long distances
Herbicide can volatilize right off plant or soil
Dependent on molecular weight of herbicide
Off-Site Movement Off-Site Movement Drift ~ DropletDrift ~ Droplet
Droplet drift is affected by
Weather conditions◦ Wind speed and direction◦ Temperature and humidity
Droplet size ◦ Nozzle type, size & height◦ Spray pressure
Carrier ◦ Type and volume
http://www.ent.iastate.edu/images/misc/spraynozzles.jpg
Influence of Droplet Size on Influence of Droplet Size on Potential Distance of DriftPotential Distance of Drift
Droplet Droplet Diameter Diameter (Microns)(Microns)
Type of DropletType of Droplet Time Time Required Required to Fall 10 to Fall 10 ft.ft.
Lateral Distance Lateral Distance Droplets Travel Droplets Travel Falling 10 ft. in 3 Falling 10 ft. in 3 mph windsmph winds
55 FogFog 66 66 min.min.
3 miles3 miles
2020 Very fine Very fine sprayspray
4.2 4.2 min.min.
1,100 ft.1,100 ft.
100100 Fine sprayFine spray 10 sec.10 sec. 44 ft.44 ft.
240240 Medium sprayMedium spray 6 sec.6 sec. 28 ft.28 ft.
400400 Coarse sprayCoarse spray 2 sec.2 sec. 8.5 ft.8.5 ft.
1,0001,000 Fine rainFine rain 1 sec.1 sec. 4.7 ft.4.7 ft.Source - University of North Dakota
Off-site Movement Off-site Movement Drift ~ Dust/GranularDrift ~ Dust/Granular
Dust and Granular Formulations◦ Dust can drift farther and for longer duration
than liquid.◦ Granular have less drift potential due to pellet
size/weight.
Image source: http://www.abc.net.au/news/image/997708-3x2-940x627.jpg
Wind Speed Indicators Wind Speed Indicators Drift Drift PotentialPotential
Field Observation Probable Wind Speed (mph)
Smoke rises, air motionless 0
Smoke drifts, air rises 1-3
Leaves quietly rustle 4-7
Leaves and twigs move 8-12
Branches move 13-18
Small trees sway 19-24
Large branches move 25-31
Whole trees move 32-38
Source: Herbicide Application Handbook. 2003. Monsanto
Chronic Exposure to Phenoxy Chronic Exposure to Phenoxy Herbicide DriftHerbicide Drift (Dicamba, 2,4-D, MCPP, etc.) (Dicamba, 2,4-D, MCPP, etc.)
Buffer StripBuffer Strip
Off-Site Movement ~ Soil WaterOff-Site Movement ~ Soil Water
Leaching◦Vertical
Run-off◦Horizontal
Off-site Movement ~ Off-site Movement ~ Leaching & Run-offLeaching & Run-off
Rainfall or irrigation water can move herbicides down through or off the soil.
Potential depends on:◦Solubility of herbicide◦Adsorption to soil
particles◦Persistence of herbicide◦Soil texture and structure ◦Amount and frequency of
rainfall/irrigation
Herbicide Movement Herbicide Movement in Soilin Soil
Herbicide Characteristics
◦ Solubility: Highly soluble herbicides are more likely to run-off or leach
Image source: http://www.elmhurst.edu/~chm/vchembook/171solublesalts.html
Herbicide Water SolubilityHerbicide Water SolubilityPesticide Solubility (mg/l)
Dichlobenil (Casoron)Dichlobenil (Casoron) 21.221.2
Benefin (Balan)Benefin (Balan) 0.10.1
Glyphosate (Round-up)Glyphosate (Round-up) 900,000900,000
2,4 - D dimethyamine2,4 - D dimethyamine 796,000796,000
Pendimethalin (Prowl)Pendimethalin (Prowl) 0.2750.275
Dicamba salt (Banvel)Dicamba salt (Banvel) 400,000400,000
Oryzalin (Surflan)Oryzalin (Surflan) 0.70.7
Trifluralin (Treflan)Trifluralin (Treflan) 0.30.3
Isoxaben (Gallery)Isoxaben (Gallery) 1.01.0
Picloram (Tordon)Picloram (Tordon) 200,000200,000
Source: OSU Extension Pesticide Properties Database
No endorsement of products intended, used for example purpose only.
Herbicide Movement Herbicide Movement in Soilin Soil
Herbicide Characteristics
Absorbency – vegetation uptake
Adsorbency – binding of a chemical to soil particles
Herbicide Movement in SoilHerbicide Movement in Soil
Herbicide Characteristics
◦ Persistence = resistance to breakdown in soil. (Half-life of herbicide in the soil)
Degradation occurs mainly in O & A Horizon
Factors influencing degradation: ◦Microbes◦Soil chemical reactions◦Sunlight/temperature
Image source: http://jupiter.plymouth.edu/~sci_ed/Turski/Courses/Earth_Science/soil_profile_diag.jpg
Persistence in SoilPersistence in SoilChemical Half-life in Months Half-life in DaysDicamba (Banvel) 2 – 6 60 - 120
Dichlobenil (Casoron) 4 – 12 120 - 360
Glyphosate (Roundup) 1 30
Pendimethalin (Prowl) 3 – 6 90 - 180
Picloram (Tordon) 6 - 18 180 - 540
Trifluralin (Treflan) 6 - 12 180 - 360
2,4-D (Weedar 64) 1 30
Oryzalin (Surflan) <1 20
Benefin (Balan) 1.5 40
Isoxaben (Gallery) 2 - 3 60 - 90
Source: http://npic.orst.edu/ingred/ppdmove.htm
No endorsement of products intended, used for example purpose only.
Herbicide Movement in Soil Herbicide Movement in Soil
Soil ProfileHerbicide Characteristics
•(Ad)Sorption Coefficient:
Image source: http://turfgrass.cas.psu.edu/education/turgeon/Modules/11_WeedManagement/Herbicide_Fate/Content/HF16.html
Herbicide Movement in SoilHerbicide Movement in Soil Soil
Characteristics
Soil texture: Sandy soils much
more prone to leaching.
Compacted clay soils are prone to runoff.
Well aggregated loamy soils reduce herbicide movement.
Image source: www.nj.nrcs.usda.gov/
Herbicide Movement in SoilHerbicide Movement in Soil
Soil Characteristics
Organic matter: Soils high in OM have: Increased microbial activity Greater water holding capacity Greater adsorption capacity
Image source: http://echezabalperiod2.wikispaces.com/file/view/Euplotespha-Ciliate_Protozoa-by_Ralf_Schmode.jpg; & http://www.teachengineering.org/view_activity.php?url=collection/nyu_/activities/nyu_permeability/nyu_permeability_activity1.xml
Herbicide Movement in SoilHerbicide Movement in Soil
Site Characteristics
Slope: Greater the slope, greater potential of herbicide movement
Awareness of Root SystemsAwareness of Root Systems
Herbicide Movement in SoilHerbicide Movement in Soil
National Pesticide Information Center◦OSU Extension Pesticide Properties Database◦Based on Solubility, Koc, and Half-life ◦Pesticide Movement Rating
Very high – Very low
http://npic.orst.edu/ingred/ppdmove.htm
National Pesticide Information Center◦Pesticide Movement Rating
◦Pendimethalin (Prowl) = Very low◦Dichlobenil (Casoron) = Moderate◦Oryzalin (Surflan) = Low◦2,4 –D amine (Weedar 64) = Moderate◦Isoxaben (Gallery) = Low◦Dicamba (Banvel) = Very high◦Picloram (Tordon) = Very high◦Glyphosate (Roundup) = Extremely low◦Benefin (Balan) = Extremely low
Herbicide Movement in SoilHerbicide Movement in Soil
Source http://npic.orst.edu/ingred/ppdmove.htm
Herbicide Injury Herbicide Injury SymptomsSymptoms
Seedling Growth Inhibitor Seedling Growth Inhibitor Herbicides Herbicides Root & Shoot ~ Stunting & DistortionRoot & Shoot ~ Stunting & Distortion
Newly planted woody plants◦ Root tips enlarge into rounded
structures and shoots can swell and be stunted.
Established woody plants◦ Stems enlarge and become brittle
http://extension.agron.iastate.edu/soybean/documents/herbicideinjury_05.pdf
Seedling Growth Inhibitor Seedling Growth Inhibitor HerbicidesHerbicides
Root & Shoot Inhibitors◦Benefin – Balan ◦Pendimethalin –
Pendulum, Prowl◦Trifluralin – Treflan◦Oryzalin – Surflan◦Isoxaben – Gallery◦Prodiamine –
Barricade
Trifluralin damage to spruce
Growth Regulator HerbicidesGrowth Regulator HerbicidesMalformed or Distorted ~ Leaves or ShootsMalformed or Distorted ~ Leaves or Shoots
Systemic herbicides
Symptoms usually on new growth
Leaf cupping, twisting or strapping of leaves, splitting or cracking of bark
Prone to drift and can move with leading edge of soil water.
Dicamba damage on Linden
Growth Regulator HerbicidesGrowth Regulator Herbicides
2,4-D, MCPP, MCPA
DicambaTriclopyr,
picloram, clopyralid
Dicamba/2,4-D Damage on Pin Oak
Phenoxy Damage on ConifersPhenoxy Damage on Conifers
2,4-D damage to pine & fir
Invasive.org, Minnesota Department of Natural Resources Archive,
Phenoxy Growth Phenoxy Growth Regulator Regulator HerbicideHerbicide
◦Irregular contours herbicide damage on honey locust trunk
(2,4-D, Dicamba, MCPP, etc.)
Herbicide Injury SymptomsHerbicide Injury SymptomsLeaf Chlorosis or NecrosisLeaf Chlorosis or Necrosis
Inhibition of photosynthesis causes various patterns of chlorosis.
Pre-emergence systemic herbicides absorbed by roots translocated to leaves.
Post emergent systemic Symptoms more severe on
side of herbicide placement.
Glyphosate damage
Leaf Chlorosis or Necrosis Leaf Chlorosis or Necrosis HerbicideHerbicide
At high rates, necrosis can occur without chlorosis.
Symptoms may persist for more than a year.
Symptoms may be confused with salt burn, drought, or freeze damage.
Picloram damage to maple
Diuron = KarmexDiruon + bromacil
= Krovar Imazapyr = ArsenalDiquat and
paraquat = Ortho Diquat, Reward
Oxyfluorfen = Goal
Paraquat Damage on Pecan; Krovar damage on Zelkova
http://www.caes.uga.edu/commodities/fruits/pecan/media/images/paraquatdamage2.JPG
Leaf Chlorosis or Necrosis Leaf Chlorosis or Necrosis HerbicidesHerbicides
Distorted Growth and ChlorosisDistorted Growth and Chlorosis
Glyphosate damage (sublethal dose)◦Chlorosis to necrosis◦Shortened internodes◦Stunted growth◦Witches broom effect◦Loss of apical
dominance◦Branch dieback
Glyphosate Damage on Rose
Case StudiesCase StudiesDichlobenil
PicloramTrifluralin
Dichlobenil Dichlobenil (Casoron) (Casoron) and the Flowering Cherry Treesand the Flowering Cherry Trees
Flowering Cherry Tree Casoron DamageFlowering Cherry Tree Casoron Damage
Picloram andPicloram andthe Curb the Curb CleanerCleaner
Trifluralin and the Conifer ConundrumTrifluralin and the Conifer Conundrum
SummarySummaryAlways Thoroughly Read & Follow All Pesticide Always Thoroughly Read & Follow All Pesticide
Label DirectionsLabel Directions
Study present & future weather conditions◦ Temperature◦ Wind speed & direction◦ Humidity◦ Rainfall
Study plants found in surrounding area◦ Identify species◦ Tree and shrub root zone
area◦ Slope
Choose herbicide to fit site conditions with considerations of potential movement
SourcesSources Washington State University. 2002. Turf & Ornamental Weed Management Principles.
MISC0170 Washington & Oregon State University & University of Idaho. 2005. Pacific Northwest
Weed Management Handbook. Starbuck, Chris. 1998. Turfgrass Research & Information Report. University of
Missouri-Columbia Turfgrass Research. http://agebb.missouri.edu/pdc/turf/report98/sesen.htm
Cornell University. 1983. Dicamba (Banvel) Herbicide Profile 10/83. http://pmep.cce.cornell.edu/profiles/herb-growthreg/
Dexter A.G. 1993. Herbicide Spray Drift A-657 (Revised). North Dakota State University & University of Minnesota http://www.ext.nodak.edu/extpubs/plantsci/weeds/a657w.htm
Ohio State University. Newsletter. Do “Drift Retardant” Chemicals Really Work? C.O.R.N. 2000 – 14. http://netc2000.tamu.edu/abstracts/tx009/paper/~corn/archive/2000/may00/00-15.html#linkg
Costello, Perry, Matheny, Henry, & Geisel. 2003. University of California. Abiotic Disorders of Landscape Plants A diagnostic Guide. Publ. 3420.
Sinclair, Lyon. & Johnson.1987. Cornell University. Diseases of Trees and Shrubs Voge, Derle, and Jenkins. 1994. Oregon State University Extension. OSU Extension
Pesticide properties Database. National Pesticide Information Center. http://npic.orst.edu/ingred/ppdmove.htm
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