Flumioxazin 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 Flumioxazin

Target PlantScientific NameUse PatternCompatible Herbicides
HydrillaHydrilla verticillataOccasionalUse with diquat
CabombaCabomba carolinianaOccasionalflumioxazin
Water lettucePistia stratiotesOccasionalflumioxazin

Table B:  Water Uses and Functions

Water Use ParametersManagement Considerations
Downstream Uses and Needs
  • Do not apply in flowing waters
  • Contact type herbicide with short half life - downstream uses minor concern
Fish and Wildlife Mgmt. 
Vegetation plantingAvoid contact and potential damage to adjacent susceptible plants - especially water lilies within application zone
Forage and preyNo issues related to this tool
Fisheries
  • Moderately toxic to fish - LC50 (96-hour) of 2.3 mg/L in rainbow trout and 21 mg/L in bluegill sunfish
  • Daphnia magna LC50 for 6 mg/L
Non-game wildlifeNo issues related to this tool
Endangered speciesNo issues related to this tool
WaterfowlNon-toxic to waterfowl - mallard duck > 2,250 mg/kg
Flood ControlNo issues related to this tool
Navigation and AccessNo issues related to this tool
IrrigationDo not use treated water for at least 5 days following application
Livestock ConsumptionThere are no restrictions on livestock consumption of treated water
Potable WaterNo potable water use restrictions
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
  • Apply approximately 200 ppb + 0.37 ppm diquat with weighted hoses to control hydrilla - see considerations for diquat if used to control hydrilla
  • Apply approximately 200 ppb to control cabomba
  • Apply < 100 ppb for water lettuce control - submersed application
  • Apply 8-12 oz / ac for water lettuce control - foliar application
Breakdown / InactivationShort half-life in water depending on season, water depth and especially pH
MicrobialMicrobial metabolism is  primary degradation pathway in soil - half life ~45 days
Adsorption

Does not bind in sediments or adsorb to soil particles

Photolysis

Susceptible to photodegradation with a half life of 3.2 days

Hydrolysis
  • Primary degradation pathway in water
  • Half-life of four days at pH = 5 and minutes at pH = 9.0 in laboratory tests
DissipationDissipation is minimal with the very short half life
Formulation 
SolidWater dispersible granular herbicide - mix with water and apply as liquid solution
Mode of Action
 
Contact
  • Inhibits protoporphyrinogen oxidase enzyme important in chlorophyll synthesis
  • Cell wall disruptor
Plant Growth RegulatorNot used as a plant growth regulator in Florida aquatic plant control applications
Stewardship 
Herbicide resistance
  • No tolerance or resistance issues for flumioxazin 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 depthImportant to know water depth to calculate appropriate concentration
Water volumeImportant to have accurate bathymetry to calculate appropriate concentration
Water movementDo not apply to flowing water
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
  • pH dependant in field tests
    • Half-life for low pH (6.0-6.2) = 39 hours, medium pH (7.0-7.2) = 18.6 h, high pH (>8.5) = 1.7 hr
    • Use buffer if tank mix water exceeds pH 7.0
    • Apply early in morning when pH is generally at lower values
Nutrient content
No issues related to this tool
Water transparencyHigher light intensity usually equates to more robust growth and therefore better control of young submersed target plants (hydrilla / cabomba)
Sediment characteristics 
Composition  
  • Sand/Clay – no issues related to this tool
  • Organic - no issues related to this tool
Potential for resuspensionDoes not bind in sediments or adsorb to suspended material in tank mix water
Plant Physiology Parameters Management Considerations
Plant origin/ growth potential 
NativeOccasional use to control cabomba at about 200 ppb
Non-nativeMay be used to control dense growths of water lilies
Invasive  
  • Increasing use to control hydrilla at about 200 ppb
  • Increasing use for selective water lettuce control
    • <100 ppb for submersed applications and 8-12 oz / ac foliar application
Plant growth stage (target/non-target)
  • Need actively growing plants for herbicide uptake
  • Mature plants more difficult to control due to higher carbohydrate reserves
Plant susceptibility (target/non-target)
  • For best hydrilla control, apply in early fall (October/November) or late winter (February/March) - lower biomass and pH likely lower
  • Water lilies in application zone may be impacted, especially when applied with diquat for hydrilla control
Potential for regrowth (target/non-target)Regrowth is rapid when applied to mature or slowly growing hydrilla
Climate Parameters Management Considerations
Weather
  • Daily
    • Needs 4-8 hours of contact for good herbicidal activity
  • Seasonally
    • Need actively growing target plants for herbicide uptake
Light intensityHigher light intensity usually equates to stronger growth and therefore better control of young submersed plants (hydrilla / cabomba)
Water temperatureNo issues related to this tool

Table D: Other Parameters

ParameterManagement Considerations
CostNo generics available
Anticipated Control Amount 
Spatial
  • Area of control is generally confined to the area to which flumioxazin is directly applied to target submersed
  • Apply at low dose with expectations of dispersal to control water lettuce
Duration
  • Hydrilla efficacy improves when applying to young actively growing plants
  • • Better efficacy during cooler weather - October/November - February/March
Time to Achieve Control
  • Floating plants
    • Needs 1-2 hours of foliar contact for control activity
    • Symptoms in 3-5 days - control in 7-14 days
  • Submersed plants
    • Needs 4-6 hours for good control activity
    • Symptoms in 7-14 days – control in 14-28 days
Contractor/Equipment
  • Foliar applications by backpack, airboat for small-scale applications to water lettuce
  • Apply with deep water trailing hoses for larger scale submersed plant control

Last updated: 13 September 2011