Carfentrazone 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 Carfentrazone

Target Plant Scientific Name Use Pattern Compatible Herbicides
Water lettuce Pistia stratiotes Infrequent  
Water hyacinth Eichhornia crassipes Infrequent Combine with 2,4-D

Table B:  Water Uses and Functions

Water Use Parameters Management Considerations
Downstream Uses and Needs Do not apply within ¼ mile upstream of functioning potable intake in rivers
Fish and Wildlife Mgmt.  
Vegetation planting No issues related to this tool
Forage and prey No issues related to this tool
Fisheries
  • Moderately toxic to fish – 96-hour LC50 = 1.6 mg/L in rainbow trout and 2.0 mg/L in bluegill sunfish
  • Daphnia magna 48-hour LC50 >10 mg/L
Non-game wildlife No issues related to this tool
Endangered species No issues related to this tool
Waterfowl Non-toxic to waterfowl – mallard duck and bobwhite quail oral LD50 >2,250 mg/kg
Flood Control No issues related to this tool
Navigation and Access No issues related to this tool
Irrigation
  • Do not use treated water for I day after application to <20% of waterbody
  • Do not use treated water for I4 days after application to >20% of waterbody
Livestock Consumption
  • Do use water for livestock consumption for I day after applying to 20-50% of waterbody
Potable Water
  • Do not apply within ¼  mile of functioning potable water intake in lakes
  • Do not apply within ¼ mile upstream of functioning potable intake in rivers
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 Apply 0.05-0.2 lbs ai/A for water lettuce control – foliar application
Breakdown / Inactivation Short half-life in water depending on season and water depth – see hydrolysis
Microbial Microbial metabolism is  primary degradation pathway in soil – half life < 1.5 days
Adsorption

Does not bind in sediments or adsorb to soil particles

Photodegradation

Susceptible to photolytic degradation

Hydrolysis

Primary degradation pathway in water – half life of 3-5 days in water

Dissipation Minimal with the very short half life and use pattern of foliar applications
Formulation  
Liquid Available as a liquid formulation which is emusifiable in water
Mode of Action
 
Contact
  • Inhibits protoporphyrinogen oxidase enzyme important in chlorophyll synthesis
  • Absorbed through the leaves
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
  • Resistance has been reported for PPO inhibitors – use rotational and active ingredient combination resistance management strategies where appropriate
Waterbody Parameters  Management Considerations
Hydrology  
Water depth Not an issue with FL use pattern – foliar applications to floating plants
Water volume Not an issue with FL use pattern – foliar applications to floating plants
Water movement Not an issue with FL use pattern – foliar applications to floating plants
Water chemistry  
Dissolved oxygen (DO)
  • Relatively fast-acting contact type herbicide
  • Controlling large area may reduce dissolved oxygen level
  • Wait 10-14 days if treating as much as half of the waterbody
pH, alkalinity, hardness
  • Not an issue with FL use pattern – foliar applications to floating plants
  • Does not bind with organic or clay particles in tank mix
Nutrient content
Not an issue with FL use pattern – small-scale floating plant management
Water transparency Not an issue with FL use pattern – foliar applications to floating plants
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
  • Does not bind in sediments or adsorb to suspended material in tank mix water
Plant Physiology Parameters  Management Considerations
Plant origin/ growth potential  
Native Not used for native plant control in Florida’s aquatic plant management program
Non-native No issues related to this tool
Invasive  
  • Occasional use to control water lettuce at 6-8 fl oz/A – depending on plant maturity
  • Occasional use to control water hyacinth at 4-8 fl oz/A – depending on plant maturity
Plant growth stage (target/non-target) Need actively growing (vs. mature) plants for optimal herbicide uptake
Plant susceptibility (target/non-target)
  • Good control of water lettuce and water hyacinth
  • Does not control adjacent knotgrass, torpedograss, pickerelweed, turfgrass
Potential for regrowth (target/non-target)
  • One application results in control of water lettuce and hyacinth
  • Regrowth from seeds
  • Injury to comingled non-target plants is minimal
Climate Parameters  Management Considerations
Weather
  • Daily
    • Needs 1-2 hours of contact for good herbicidal activity
  • Seasonally
    • Need actively growing target plants for herbicide uptake
Light intensity Not an issue with FL use pattern – foliar applications to floating plants
Water temperature Not an issue with FL use pattern – foliar applications to floating plants

Table D: Other Parameters

Parameter Management Considerations
Cost
  • No generics available
  • Generally more expensive than 2,4-D or diquat
  • Economic benefit when used as additional tool to rotate or apply in combination with other herbicides for resistance management
Anticipated Control Amount  
Spatial Area of control is generally confined to the area to which carfentrazone is directly applied to target floating plants
Duration Efficacy improves when applying to young actively growing plants
Time to Achieve Control
  • Floating plants
  • Rainfast in 15 minutes
  • Symptoms in 2-5 days – control in 3-4 weeks
Contractor/Equipment
  • Foliar applications by backpack, airboat for small-scale applications to water lettuce and water hyacinth
  • Apply with adjuvant to increase coverage on leaf surfaces
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