| Herbicide Rate | - Generally applied at 1-5 ppm for submersed aquatic plant control:
- 1-3 ppm for hydrilla and Eurasian water milfoil control
- 1-5 ppm for coontail and crested water lily
- 5 ppm for hygrophila control
|
| Breakdown / Inactivation | Half-life is generally 3-7 days |
| Microbial | Primary degradation pathway - degradation rate is water-temperature dependant |
| Adsorption | Does not adsorb onto soils |
Photolysis
| Not broken down via photolysis |
| Dissipation | - Highly soluble so disperses in water
- Higher rates may be necessary when applying in narrow bands or small areas where water movement may be expected (i.e. reservoirs)
|
| Formulation | |
| Liquid | Available in liquid formulation |
| Solid | Available in solid (granular polymer) formulation |
Mode of Action
| |
| Contact herbicide | - Interferes with protein and lipid synthesis; disrupts cell membrane and respiration
- Somewhat mobile in plant tissues
|
| Plant Growth Regulator | Not used as a plant growth regulator in Florida aquatic plant control applications |
| Stewardship | |
| Herbicide resistance / tolerance | - Increasing tolerance identified in hydrilla at two sites in Florida
- Potassium endothall combined with diquat proved effective in controlling tolerant hydrilla
- Rotate or use with diquat, fluridone, penoxsulam, or imazamox where appropriate
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| Waterbody Parameters | Management Considerations |
| Hydrology | |
Water depth
| No issues related to this tool, when used for floating and emergent plant control |
| Water volume | - See label chart when applying for submersed plant control
- Accurate bathymetry is essential to calculate appropriate concentration
|
| Water movement | Apply higher rates or combine with diquat for control where water movement is anticipated |
| Water chemistry | |
| Dissolved oxygen (DO) | Use caution for larger applications to control dense hydrilla surface mats in warm water to avoid DO depletion |
| pH, alkalinity, hardness | No issues related to this tool |
Nutrient content
| - Relatively fast-acting herbicide
- Hydrilla mats generally decline in 2-3 weeks after application
- Nutrients may be released from decomposing plants in large treatments
|
| Water transparency | - Hydrilla may recover more quickly in clear waters
- May get extended submersed plant control in tannic or turbid waters where low light levels inhibit recovery
|
| Sediment characteristics | |
Composition
| - Sand/Clay – no issues related to this tool
- Organic – no issues related to this tool, does not adhere to organic material
|
| Potential for resuspension | No issues related to this tool, does not adhere to organic material |
| Plant Physiology Parameters | Management Considerations |
| Plant origin/ growth potential | |
| Native | Occasional use for coontail control |
| Non-native | Occasional use to control Eurasian water milfoil and crested water lily |
| Invasive | - Spot control control water hyacinth and water lettuce
- Frequent use to control hydrilla
- Occasional use to control hygrophila
|
| Plant growth stage (target/non-target) | - Need actively growing plants for herbicide uptake
- Use lower rates to control young actively growing plants such as hydrilla
- Increase selectivity by controlling hydrilla in fall / winter when native plants are senescing or dormant
- Higher rates are required to control mature surface-matted hydrilla
- Plants usually have higher carbohydrate reserves
- Plants may not be as actively growing
- Microbes degrade endothall more quickly in warm water, requiring higher dose
|
Plant susceptibility (target/non-target)
| - Apply to actively growing target plants
- Apply to entire water column at 3-4 ppm for crested water lily control
- Hydrilla control - use endothall alone or combine with other active ingredients
- Apply at 1.5-2.0 ppm when used alone for large-scale hydrilla control
- Use 3 ppm or higher for spot or band application to account for dissipation
- Control robust hydrilla with endothall; apply fluridone to control regrowth
- Apply fluridone and spot control surviving hydrilla with endothall
- Apply generally at 1.5 ppm + 20 ppb penoxsulam
- Apply 1.0-2.0 ppm endothall + diquat up to 0.37 ppm for rapid control
- Selective control of hydrilla growing among eelgrass (Vallisneria americana)
|
| Potential for regrowth (target/non-target) | - Hydrilla regrowth depends on impact on root crowns, water clarity and depth
- Regrowth is slower if root crowns killed; limited to tuber/turion sprouting
- Native southern naiad (Najas guadalupensis) and Illinois pondweed (Potamogeton illinoensis) are controlled by potassium endothall, but usually recover
|
| Climate Parameters | Management Considerations |
| Weather | - Daily
- Need at least 24 hours of contact for hydrilla control
- Dependant on dose and water temperature
- Windy conditions may increase dissipation in spot or band applications
- Seasonal
- Less herbicide may be required in cooler months
- Microbial breakdown is slower so herbicide is active for longer period
- Increased uptake by actively growing plants in late winter / early spring
|
| Light intensity | No issues related to this tool - not broken down via photolysis |
| Water temperature | Potassium endothall degradation can occur more rapidly in warmer water (80º) which could result in reduced efficacy |
