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 3-13 fl oz/A Occasional use to control water hyacinth at 7-15 fl oz/A
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

Last updated: 13 September 2011

Plant Management in Florida Waters : An Integrated Approach