Center For Aquatic And Invasive Plants

Imazamox 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 Imazamox

Target Plant	Scientific Name	Use Pattern	Compatible Herbicides
Cattail	Typha spp.	Frequent	Applied alone
Uruguayan primrose willow complex	Ludwigia grandiflora / hexapetala	Frequent	Alone or with carfentrazone
Primrose willow	Ludwigia octovalvis / peruviana	Common	Alone or with carfentrazone
Water hyacinth	Eichhornia crassipes	Occasional	Alone or with carfentrazone
Wild taro	Colocasia esculenta	Spot control	Applied alone

Table B: Water Uses and Functions

Water Use Parameters	Management Considerations
Downstream Uses and Needs	See irrigation and potable water parameters below
Fish and Wildlife Mgmt.
Vegetation planting	Avoid applications within newly planted aquatic revegetation sites
Forage and prey	No issues related to this tool
Fisheries	Practically non-toxic to fish Fathead minnow LC₅₀ – 96hr > 122 ppm Bluegill LC₅₀ – 96hr > 119 ppm
Non-game wildlife	No issues related to this tool
Endangered species	No issues related to this tool
Waterfowl	Practically non-toxic to birds Mallard duck dietary tests LC₅₀ > 5,500 ppm
Flood Control	Need to minimize flow for at least 48 hours to allow good contact
Navigation and Access	No issues related to this tool
Irrigation	No turf irrigation restrictions Wait 24 hours before irrigating crops if applied within 100 feet of intake at concentrations > 75 ppb Approved for food crop irrigation after concentration drops below 75 ppb
Livestock Consumption	No issues related to this tool
Potable Water	No restrictions for applications made 1/4 mile or more from active potable water intake Shut down water intake if application exceeds 50 ppb within ¼ mile of potable water intake
Recreation
Boating	No issues related to this tool
Fishing	No fishing restrictions
Hunting	No issues related to this tool
Swimming	No swimming restrictions

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

Herbicide Parameters	Management Considerations
Herbicide Rate	Maximum rates Submersed applications – 500 ppb (173 fl oz / ac ft) Foliar broadcast – 1 gpa Spot applications – up to 5% by volume Generally applied at: 8-16 oz / ac for water hyacinth control ~32 oz / ac for primrose willow and cattail control
Breakdown / Inactivation
Microbial	Not sensitive to microbial breakdown
Adsorption	Weakly adsorbed to clay and organic particles
Photolysis	Broken down by sunlight – primary pathway
Hydrolysis	Not sensitive to hydrolysis
Dissipation	Soluble in water May dissipate widely in submersed applications depending on water movement Herbicidal activity only in areas where concentration is sufficient to control target plant
Formulation
Liquid	Available in liquid formulation
Solid	Available in granular formulation Granular formulation used for spot and large-scale submersed plant applications
Mechanism of Action	Classified in WSSA Resistance Grouping #2 Acetolactate synthase (ALS) enzyme inhibitor
Mode of Action
Systemic	Quickly absorbed by leaves and shoots Moves to areas of new growth Shuts down plant growth almost immediately Acts like contact herbicide in this regard Control may take 2-6 weeks Prevents the formation of essential branched chain amino acids in plants – ALS Without these essential amino acids, the plant cannot make proteins, enzymes, etc. Plant cannot continue growing and eventually starves and dies
Plant Growth Regulator	Not currently used as a plant growth regulator in FWC programs Functions as growth inhibitor or growth regulator at lower rates of 50-150 ppb May provide 3-6 months growth suppression at lower rates
Stewardship
Herbicide resistance	Resistance to ALS compounds confirmed in terrestrial species No resistance reported in Florida aquatic plants Rotate other compounds for successive control applications, or Use in combination with other active ingredients
Waterbody Parameters	Management Considerations
Hydrology
Water depth	Amounts used for submersed applications are depth dependent – see label for chart
Water volume	Accurate bathymetry is required to calculate prescribed dose for submersed plant applications Apply if possible when water level (volume) is lower
Water movement	Need at least 2-3 days of exposure for submersed applications Similar to potassium endothall
Water chemistry
Dissolved oxygen (DO)	DO sags not likely an issue with current FWC small-scale use patterns
pH, alkalinity, hardness	No issues related to this tool
Nutrient content	Slow acting herbicide so nutrient release from decomposing plants is slow
Water transparency	Color/tannic content – no issues related to this tool Turbidity – no issues related to this tool
Sediment characteristics
Composition	Sand/Clay – no issues related to this tool Organic – do not apply granular formulation to flocculent organic sediments
Potential for re-suspension	No issues related to this tool
Plant Physiology Parameters	Management Considerations
Plant origin / growth potential
Native	Cattail Applied at rates of 16-32 oz / ac with methylated seed oil adjuvant Very active on cattail 32 fl oz / ac for selective, but slow (~3 months) control when mixed with bulrush 64 fl oz / ac for effective control of monocultures, but less selective 32 fl oz / ac + 32 fl oz / ac glyphosate for excellent monoculture control, but non-selective Much better selectivity than glyphosate or imazapyr alone
Non-native	Primrose willow (Ludwigia peruviana) Applied alone at 32 oz / ac Combined at 32 oz / ac imazamox + 4 oz / ac carfentrazone
Invasive	Uruguayan primrose willow complex Applied foliarly alone at 32 oz / ac Combined at 32 oz / ac imazamox + 4 oz / ac carfentrazone Submersed application – 400 ppb for Rosette growth stage or emergent plants less than 15″ tall Water hyacinth Applied foliarly at 8-16 oz / ac May take 2-4 weeks for control Wild taro Extremely active on wild taro Applied at 96-128 oz / ac
Plant growth stage (target/non-target)	Lower rates may have greater impact on young actively growing plants
Plant susceptibility (target/non-target)	Must be applied to actively growing target plants
Potential for regrowth (target/non-target)	May provide more than 1-year control of floating plants during in-water applications
Climate Parameters	Management Considerations
Weather	Daily Apply when wind / wave action is calm for submersed applications Seasonally Apply to actively growing plants
Light intensity	Intense sunlight may accelerate photolytic breakdown
Water temperature	Apply with water temperature generally above 50º F to ensure active growth of target plants Plants must be actively growing to take up herbicide

Table D: Other Parameters

Parameter	Management Considerations
Cost	Generics are not available
Anticipated Control Amount
Spatial	Submersed applications will disperse outside treatment area depending on water movement Minimize dispersal for submersed applications using granular formulations
Duration
Time to Achieve Control	Relatively slow acting Growth ceases almost immediately after application Symptoms are slow to express Control may take 2-6 weeks
Contractor/Equipment	Apply by hand gun and airboat for small acreages Or by helicopter for larger acreages of floating and emergent plants