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 Plant Scientific Name Use Pattern Compatible Herbicides
Alligatorweed Alternanthera philoxeroides Spot Use with non-ionic surfactant
Brazilian pepper Schinus terebinthifolius Spot Use with methylated seed oil
Primrose willow Ludwigia peruviana Spot Use with non-ionic surfactant

Table B: Water Uses and Functions

Water Use Parameters Management Considerations
Downstream Uses and Needs Minimize overspray to banks or shorelines of moving water sites
Fish and Wildlife Mgmt.  
Vegetation planting Avoid drift and potential damage to adjacent susceptible plants
Forage and prey No 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 wildlife No issues related to this tool
Endangered species Avoid drift and potential damage to susceptible plants in endangered species habitat
Waterfowl Non-toxic to waterfowl – mallard duck LC50 >5,000 ppm
Flood Control No issues related to this tool
Navigation and Access No issues related to this tool
Irrigation Do 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  
Boating No issues related to this tool
Fishing No fish consumption restriction
Hunting No issues related to this tool
Swimming No swimming restriction

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

Herbicide Parameters Management 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 / Inactivation Short half-life in water depending on season and water depth – see photolysis
Microbial Microbial 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  
Liquid Available in liquid formulation
Solid Available 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 Regulator Not 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 depth No issues related to this tool, not used for submersed plant control in Florida
Water volume No issues related to this tool, not used for submersed plant control in Florida
Water movement No 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, hardness No 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 transparency No 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  
Native Occasional use to control frog's bit or floating tussocks 3-8 qt / acre
Non-native Occasional 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 intensity No issues related to this tool, not used for submersed plant control in Florida
Water temperature No issues related to this tool, not used for submersed plant control in Florida

Table D: Other Parameters

Parameter Management Considerations
Cost Generics available
Anticipated Control Amount  
Spatial Area of control is generally confined to the area to which triclopyr is directly applied to target emergent or floating plants
Duration Kills roots of susceptible plants allowing longer control than herbicides that only kill standing crop
Time to Achieve Control Symptoms in as little as 24 hours, complete kill in several weeks after application
Contractor/Equipment Foliar applications by backpack for spot control, airboat or ATV for small-scale applications
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