Center For Aquatic And Invasive Plants

Flumioxazin Considerations

*Important: See Reference Guide Beforehand

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.

These considerations are not meant to replace or contradict the EPA approved label.
Always read and follow the pesticide label for each product used.

Table A: Herbicide Use Patterns for Flumioxazin

Target Plant	Scientific Name	Use Pattern	Compatible Herbicides
Water lettuce	Pistia stratiotes	Frequent	Alone for water lettuce – with 2,4-D or penoxsulam when mixed with water hyacinth
Cuban club-rush	Cyperus blepharoleptos	Frequent	Combine with glyphosate
Ludwigia uraguayensis complex	Ludwigia grandiflora & L. hexapetala	Frequent	Combine with glyphosate Occasionally 2,4-D or imazamox
Hydrilla	Hydrilla verticillata	Occasional	Alone or combine with diquat or potassium endothall
Ambulia	Limnophila sessiliflora	Occasional	Alone or with diquat
Fanwort	Cabomba caroliniana	Occasional	Alone or with diquat

Table B: Water Uses and Functions

Water Use Parameters	Management Considerations
Downstream Uses and Needs	For use in slow moving or quiescent waters Do not apply in intertidal areas or estuaries Downstream uses minor concern Contact type herbicide with short half- life
Fish and Wildlife Mgmt.
Vegetation planting	Avoid contact and potential damage to adjacent susceptible plants Especially water lilies within application zone
Forage and prey	No issues related to this tool
Fisheries	Moderately toxic to fish LC₅₀ (96-hour) = 2.3 mg/L in rainbow trout and 21 mg/L in bluegill sunfish Daphnia magna LC₅₀ = 6 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 LC₅₀ > 2,250 mg/kg
Flood Control	No issues related to this tool
Navigation and Access	No issues related to this tool
Irrigation	Irrigation restrictions from 0-5 days may apply for turf and ornamental plants See label for application method, rate and depth for possible restriction
Livestock Consumption	There are no restrictions on livestock consumption of treated water
Potable Water	No potable water use restrictions
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	See plant physiology parameter considerations below for current rates by plant species 50-200 ppb for submersed applications 2-8 oz/ac for foliar applications
Breakdown / Inactivation	Short half-life in water depending on season, water depth and especially pH
Microbial	Microbial metabolism is the 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 days
Hydrolysis	Primary degradation pathway in water – especially sensitive in low pH waters Half-life of four days at pH = 5 and minutes at pH = 9.0 in laboratory tests
Dissipation	Dissipation is minimal with the very short half-life
Formulation
Liquid	Not available in aqueous formulation
Solid	Water dispersible granular herbicide Mix with water and apply as liquid solution
Mechanism of Action	Classified in WSSA Resistance Grouping #14 Protoporphyrinogen oxidase (PPO) enzyme inhibitor
Mode of Action
Contact	Inhibits protoporphyrinogen oxidase enzyme important in chlorophyll synthesis Absorbed through the leaves – does not move in the plant Causes formation of a light-absorbing chlorophyll precursor outside of the chloroplast This compound absorbs energy from sunlight, but cannot pass through the Z-scheme Energy is passed on to oxygen, creating radical oxygen and cell membrane disruption
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 in terrestrial applications Rotate or combine with other active ingredient where appropriate
Waterbody Parameters	Management Considerations
Hydrology
Water depth	Important to know water depth to calculate appropriate concentration for submersed applications
Water volume	Important to have accurate bathymetry to calculate appropriate concentration for submersed applications
Water movement	Do not apply to flowing water Can be used in slow moving, quiescent waters
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	Half-life is pH dependent in field tests Low pH (6.0-6.2) = 39 hours Medium pH (7.0-7.2) = 18.6 hours High pH (>8.5) = 1.7 hours Use buffer if tank mix water exceeds pH 7 Apply submersed applications early in morning when pH is generally at lower values
Nutrient content	No issues related to this tool
Water transparency	Higher light intensity usually equates to more robust growth of submersed target plants
Sediment characteristics
Composition	Sand/Clay – no issues related to this tool Organic – no issues related to this tool
Potential for re-suspension	No issues related to this tool Does not adsorb to suspended material in water body or in tank mix water
Plant Physiology Parameters	Management Considerations
Plant origin / growth potential
Native	Fanwort Use to control cabomba at about 200 ppb Cabomba usually present in lower pH waters
Non-native	Ambulia (Limnophila sessiliflora) Alone at 200 ppb Combination of flumioxazin at 100 ppb + diquat at 370 ppb Very active on water lilies at this rate
Invasive	Water lettuce 2-4 oz / ac applied foliarly 50 ppb for submersed application to control water lettuce Need an area >15 ac to compensate for dissipation Hydrilla (and Hygrophila (Hygrophila polysperma)) Alone at 200 ppb Combination of flumioxazin at 100 ppb + diquat at 370 ppb Ludwigia grandiflora and torpedograss control at 4 oz / ac + 7.5 pt / ac glyphosate Increasing use for selective water lettuce control ~50 ppb for submersed applications and 2-8 oz / ac foliar application 4 oz / ac + 4 oz / ac penoxsulam for water lettuce / water hyacinth mix Ludwigia uraguayensis complex and Cuban club-rush 4 oz flumioxazin + 96-120 oz glyphosate / ac Adding flumioxazin accelerates knockdown – unclear if it increases efficacy
Plant growth stage (target/non-target)	Need actively growing plants for herbicide uptake Mature plants are more difficult to control due to higher carbohydrate reserve
Plant susceptibility (target/non-target)	Good alternative to diquat for controlling water lettuce mixed with bulrush Does not cause bulrush stem spotting or browning associated with diquat applications Foliar applications when wind speed < 10 mph to reduce damage from drift Apply in early fall (Oct/Nov) or late winter (Feb/Mar) for best hydrilla control 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)	Thorough water lettuce control Regrowth from seed or new plants flushed into control zone Regrowth is rapid when applied to mature or slowly growing hydrilla Must kill root crowns to slow regrowth from tubers
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 intensity	Higher light intensity usually equates to stronger growth and therefore better control of young submersed plants (hydrilla / cabomba)
Water temperature	No issues related to this tool

Table D: Other Parameters

Parameter	Management Considerations
Cost	No generics available Similar chemistry available in carfentrazone Not as much operational monitoring or use of carfentrazone
Anticipated Control Amount
Spatial	Area of submersed plant control (hydrilla, cabomba, limnophila, hygrophila) is generally confined to the area to which flumioxazin is directly applied Low-dose submersed applications 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 Longer control duration when root crowns killed
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 Shallow hose for submersed application to control water lettuce Apply with deep water trailing hoses for larger scale submersed plant control