Triclopyr Considerations

No single herbicide is appropriate for controlling all invasive aquatic plants (or nuisance growths of native aquatic plants), in all situations. A herbicide may perform differently depending on the waterbody, its use, the time of year—or even the time of day. Therefore, aquatic plant managers must have a thorough understanding of how each herbicide acts in Florida aquatic systems. The following parameters are evaluated when considering this herbicide to manage aquatic plants in a specific waterbody. Each parameter is linked to an explanation and examples are provided to demonstrate their relevance to developing comprehensive aquatic plant management strategies.

Table A:  Herbicide Use Patterns for Triclopyr

Target PlantScientific NameUse PatternCompatible Herbicides
AlligatorweedAlternanthera philoxeroidesSpotUse with non-ionic surfactant
Brazilian pepperSchinus terebinthifolius SpotUse with methylated seed oil
Primrose willowLudwigia peruviana SpotUse with non-ionic surfactant

Table B:  Water Uses and Functions

Water Use ParametersManagement Considerations
Downstream Uses and NeedsMinimize overspray to banks or shorelines of moving water sites
Fish and Wildlife Mgmt. 
Vegetation plantingAvoid drift and potential damage to adjacent susceptible plants
Forage and preyNo issues related to this tool
Fisheries
  • Formulated triclopyr non-toxic to fish - LC50 (96-hour) of 552 mg/L in rainbow trout and 891 mg/L in bluegill sunfish
  • Daphnia magna LC50 for the amine salt = 1170 mg/L
Non-game wildlifeNo issues related to this tool
Endangered speciesAvoid drift and potential damage to susceptible plants in endangered species habitat
WaterfowlNon-toxic to waterfowl - mallard duck LC50 >5,000 ppm
Flood ControlNo issues related to this tool
Navigation and AccessNo issues related to this tool
IrrigationDo not use treated water for 120 days following application, or until the triclopyr level in the intake water is determined by laboratory analysis to be I.0  ppb or less
Livestock Consumption
  • There are no restrictions on livestock consumption of treated water
  • Do not allow lactating dairy animals to graze treated areas until the next growing season
Potable Water
  • Setback distances from functioning potable water intakes are variable depending on size and rate of  application - consult label for specifics
  • To apply within setback distances, the intake must be shut off until the triclopyr level at the water intake is determined to be 0.4 ppm or less
Recreation 
BoatingNo issues related to this tool
FishingNo fish consumption restriction
HuntingNo issues related to this tool
SwimmingNo swimming restriction

Table C:  Herbicide, Waterbody, Plant, and Climate Parameters

Herbicide ParametersManagement Considerations
Herbicide Rate
  • Foliar applications generally at 3-8 quarts / acre  with non-ionic surfactant
  • Basal bark applications generally at 10 % solution with methylated seed oil
Breakdown / InactivationShort half-life in water depending on season and water depth - see photolysis
MicrobialMicrobial metabolism is  primary degradation pathway in soil - half life ~45 days
Adsorption

Does not bind strongly or adsorb to soil particles

Photolysis
  • Primary degradation pathway in water
  • Half-life of 2.5 days (shallow water/summer) to 14 days (deep/winter)
Dissipation
  • Not used to control submersed plants in Florida - not applied directly to water
  • Does not adsorb to soils - may be more persistent and more mobile in soils
Formulation 
LiquidAvailable in liquid formulation
SolidAvailable in solid formulation mixed with 2,4-D amine salt
Mode of Action
 
Systemic herbicide
  • Interferes with normal expansion and division of plant cells
    • Symptoms include cupped leaves and twisted stems
  • Root or foliar uptake - translocates throughout plant tissues
Plant Growth RegulatorNot used as a plant growth regulator in Florida aquatic plant control applications
Stewardship 
Herbicide resistance
  • No tolerance or resistance issues reported in Florida
  • Rotate or use with 2,4-D, imazapyr, or glyphosate where appropriate
Waterbody Parameters Management Considerations
Hydrology 
Water depthNo issues related to this tool, not used for submersed plant control in Florida
Water volumeNo issues related to this tool, not used for submersed plant control in Florida
Water movementNo issues related to this tool, not used for submersed plant control in Florida
Water chemistry 
Dissolved oxygen (DO)
  • No issues related to this tool, not used for submersed plant control in Florida
  • Fairly slow acting herbicide used for shoreline applications and spot control within secluded marshes where DO is less concern
pH, alkalinity, hardnessNo issues related to this tool
Nutrient content
  • No issues related to this tool, not used for submersed plant control in Florida
  • Fairly slow acting herbicide used for shoreline applications and spot control within secluded marshes
Water transparencyNo issues related to this tool, not used for submersed plant control in Florida
Sediment characteristics 
Composition  
  • Sand/Clay – no issues related to this tool
  • Organic – no issues related to this tool
Potential for resuspension
  • No issues related to this tool
    • Not used for submersed plant applications in Florida
    • Does not readily adsorb to suspended material in tank mix water
Plant Physiology Parameters Management Considerations
Plant origin/ growth potential 
NativeOccasional use to control frog's bit or floating tussocks 3-8 qt / acre
Non-nativeOccasional use to control primrose willow, alligatorweed - 3-5 qt / acre
Invasive  
  • Occasional use to control Brazilian pepper with methylated seed oil
    • 1% solution for foliar applications
    • 10% solution for basal bark applications
Plant growth stage (target/non-target)Need actively growing plants for herbicide uptake
Plant susceptibility (target/non-target)
  • Auxin-like activity
    • Controls woody and broadleaf plants
    • Most grasses and other monocots are tolerant
  • Apply to actively growing target plants
  • Apply when potential for drift is minimal to avoid damage to non-target plants
Potential for regrowth (target/non-target)Kills roots of susceptible plants allowing longer control than herbicides that only kill standing crop
Climate Parameters Management Considerations
Weather
  • Daily
    • Rainfast in about two hours after application
    • May damage adjacent woody or susceptible broadleaf plants due to drift
      • Subject to FL DACS organo-auxin rule - 5E-2.033 F.A.C.
      • Applications prohibited in winds above 10 mph
  • Seasonally
    • Selectivity is increased controlling Brazilian pepper in winter when non-target plants like buttonbush are dormant
Light intensityNo issues related to this tool, not used for submersed plant control in Florida
Water temperatureNo issues related to this tool, not used for submersed plant control in Florida

Table D: Other Parameters

ParameterManagement Considerations
CostGenerics available
Anticipated Control Amount 
SpatialArea of control is generally confined to the area to which triclopyr is directly applied to target emergent or floating plants
DurationKills roots of susceptible plants allowing longer control than herbicides that only kill standing crop
Time to Achieve ControlSymptoms in as little as 24 hours, complete kill in several weeks after application
Contractor/EquipmentFoliar applications by backpack for spot control, airboat or ATV for small-scale applications

Last updated: 13 September 2011