| Herbicide Rate | Maximum label concentration for controlling hydrilla is 500 ppb per growing season- Generally applied at 150-250 ppb for hydrilla control
- Generally applied at 50-150 ppb hydrilla growth regulation
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| Breakdown / Inactivation | Average half life in water of 14 days in Florida |
| Microbial | N/A |
| Photolysis | Broken down by sunlight – primary pathway |
| Dissipation | Soluble - weakly adsorbed to clay and organic particles- May dissipate widely in submersed plant applications depending on water movement
- Herbicidal activity only in areas where concentration is sufficient to control the target plant
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| Formulation | |
| Liquid | Available as a liquid formulation |
| Granular | |
| Mode of Action | |
| Systemic | - Quickly absorbed by leaves, shoots, and roots - translocated to meristematic tissue
- Shuts down plant growth almost immediately - control in 2-6 weeks
- Inhibits the plant enzyme acetolactate synthase (ALS) - inhibits cell division and causes plant death
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| Plant Growth Regulator | - Primarily used as herbicide for aquatic plant control at rates of 150-250 ppb
- Functions as growth inhibitor or growth regulator at lower rates of 50-150 ppb
- May provide 3-6 months growth suppression at lower rates
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| Stewardship | |
| Herbicide resistance / tolerance | - Resistance to ALS compounds confirmed in terrestrial species - none in aquatics
- Rotate other compounds for successive large-scale hydrilla control applications, or
- Use in combination with other active ingredients including potassium endothall or penoxsulam for submersed plant control
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| Waterbody Parameters | Management Considerations |
| Hydrology | |
Water depth
| Amounts used are depth dependent – see label for chart |
| Water volume | - Accurate bathymetry is required to calculate prescribed dose for submersed plant control
- Apply if possible when water level (volume) is lower
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| Water movement | Need at least 2-3 days of exposure for submersed plant control - similar to potassium endothall |
| Water chemistry | |
| Dissolved oxygen (DO) | - Relatively fast acting when used alone and in combination with potassium endothall for submersed plant control
- DO sags not likely an issue, especially in fall-spring applications
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| pH, alkalinity, hardness | No issues related to this tool |
Nutrient content
| Slow acting herbicide so nutrient release from decomposing plants in large-scale control is slow |
| Water transparency | - Color/tannic content – no issues related to this tool
- Turbidity – no issues related to this tool
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| Sediment characteristics | |
Composition
| - Sand/Clay – no issues related to this tool
- Organic – do not apply granular formulation to flocculent organic sediments
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| Potential for resuspension | No issues related to this tool |
| Plant Physiology Parameters | Management Considerations |
| Plant origin/ growth potential | |
| Native | Used for pennywort, cattail and frog’s bit control |
| Non-native | Used for primrose willow and phragmites control |
| Invasive | - Increasing use for hydrilla, alligator weed, hygrophila, and water hyacinth
- Frequent use for wild taro and Chinese tallow control
- Controls water hyacinth through root uptake in submersed plant applications, and by direct foliar application
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| 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
- Good efficacy for hydrilla control
- When applied at rates of 150-250 ppb during periods of active plant growth
- Occasional use in combination with potassium endothall to control small to large-scale hydrilla in quiescent waters
- Imazamox rate of 75-150 ppb / potassium endothall rate of 1-2 ppm
- Control is relatively fast - 2-6 weeks
- Controls some beneficial submersed plants like Illinois pondweed (Potamogetom illinoensis) during season of treatment
- Does not control southern naiad (Najas guadalupensis)
- Good efficacy for wild taro, alligator weed, and Chinese tallow control
- Up to 1 gpa for foliar broadcast and up to 5% solution plus surfactant for spot control
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| Potential for regrowth (target/non-target) | - Effective for annual control of hydrilla when applied alone or in combination with potassium endothall
- Regrowth mostly from sprouting turions / tubers
- Hydrilla control varies with season and plant growth stage – up to 1 year control
- Older plants with more carbohydrate reserves will require higher dose of imazamox
- May provide more than 1 year control of floating plants during in-water applications
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| Climate Parameters | Management Considerations |
| Weather | - Daily
- Apply when wind / wave action is calm
- Seasonal
- Optimum hydrilla control efficacy when applied during active plant growth periods
- Extended hydrilla treatment window when applied with potassium endothall for fall or winter-spring applications
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| Light intensity | Low intensity reduces submersed plant (hydrilla) ability to recover |
| Water temperature | - Apply with water temperature generally above 50º F to ensure active growth of target plants
- Plants must be actively growing for plant to take up herbicide
- Apply throughout water column for hydrilla control if strong thermocline exists
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