| Herbicide Rate |
- Generally applied at 1-5 ppm for submersed aquatic plant control:
- 1-3 ppm for hydrilla control
- 3-5 ppm for coontail control
- 3 ppm potassium endothall + 0.3 ppm amine endothall to control crested floating heart
|
| Breakdown / Inactivation |
- Half-life is generally 3-7 days
|
| Microbial |
- Primary degradation pathway
- Degradation rate is water-temperature and plant density dependent
|
| Adsorption |
- Does not adsorb to suspended solids or sediments
|
| Photolysis |
- Does not degrade by photolysis
|
| Hydrolysis |
- Not sensitive to hydrolysis
|
| Dissipation |
- Highly soluble so disperses in water
- Higher rates may be necessary when:
- Applying in narrow bands or small areas, or
- Where water movement may be expected (i.e. reservoirs, canals, springs)
|
| Formulation |
|
| Liquid |
- Available in liquid formulation
- Can be used as surface or sub-surface application
- Achieves uniform concentration throughout water column within a few hours
|
| Solid |
- Available in solid (granular polymer) formulation
- Granules offer good substitute where liquid potassium endothall formulation is impractical
- Spot control of new hydrilla infestations at boat ramps or along shorelines
- Sequential daily applications for hydrilla control in flowing water (e.g., spring runs)
- Aerial applications among emergent plants to avoid non-target spotting
- Disperses throughout water column in treatment zone within a few hours
|
| Mechanism of Action |
- Unclassified in WSSA Resistance Grouping
- Protein phosphatase inhibitor
|
| Mode of Action |
|
| Systemic |
- Absorbed by foliage or underwater tissues
- Interferes with protein and lipid synthesis
- Disrupts cell membrane and respiration – cell membranes become leaky
- Cell contents spill out – cannot make energy and die
- Somewhat mobile in plant tissues
- Long thought to be contact-type herbicide
- Fast-acting
|
| Plant Growth Regulator |
- Not used as a plant growth regulator in Florida aquatic plant control applications
|
| Stewardship |
|
| Herbicide resistance |
- Not yet classified in WSSA Resistance Grouping
- Increased tolerance identified in hydrilla at two sites in Florida
- Potassium endothall combined with diquat effectively controlled tolerant hydrilla
- Rotate or use with other active ingredients where appropriate
- Compatible herbicides include: bispyribac, diquat, fluridone, penoxsulam, topramezone
|
| Waterbody Parameters | Management Considerations |
|---|
| Hydrology |
|
| Water depth |
- Important to know water depth to calculate appropriate dose
- Potassium endothall is used to dose water column for submersed plant control
|
| Water volume |
- Accurate bathymetry is essential to calculate appropriate concentration
- See label chart when applying for submersed plant control
|
| Water movement |
- Need 12-24 hours of exposure for crested floating heart or hydrilla control
- Apply higher rates or combine with contact herbicide where water movement is anticipated
|
| Water chemistry |
|
| Dissolved oxygen (DO) |
- Caution when controlling large, dense hydrilla stands in warm water to avoid DO depletion
- Particularly when combined with diquat
|
| pH, alkalinity, hardness |
- No issues related to this tool
|
| Nutrient content |
- Relatively fast-acting herbicide
- Hydrilla mats generally decline in 1-3 weeks after application
- Nutrients may be released from decomposing plants in large treatments
|
| Water transparency |
- Hydrilla may recover more quickly in clear or shallow waters
- May get extended submersed plant control in deep, tannic or turbid waters
- 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 re-suspension |
- No issues related to this tool, does not adhere to organic material
|
| Plant Physiology Parameters | Management Considerations |
|---|
| Plant origin / growth potential |
|
| Native |
- Occasionally applied to control some native submersed plants at 3-5 ppm
- Coontail (Ceratophyllum demersum), southern naiad (Najas guadalupensis), Illinois pondweed (Potamogeton illinoensis)
|
| Non-native |
- Little to no control reported with this compound for non-native plant management in Florida
|
| Invasive
|
- Crested floating heart
- Use alone or in conjunction with amine endothall
- Primary control method for crested floating heart
- Follow-up applications may be necessary to control skips
- Alone at 2 qt/acre-foot as subsurface injection
- Apply to actively growing plants late summer (July – August)
- Combination at 3.0 ppm with amine endothall at 0.3 ppm
- Apply late spring through summer
- Hydrilla
- Most frequently used herbicide for hydrilla control
- Used alone or with other herbicides
- Best results when applied to young, actively growing plants in cooler water
- Apply to control zone quickly to avoid loss from dissipation and degradation
- Applied at 3 ppm
- For small plots or bands of plants where some dissipation is anticipated
- For mature plants with high carbohydrate reserves
- In late season control when growth is slower
- In dense plants stands and warm water
- Where microbial degradation of endothall is more rapid
- Applied at 2 ppm for larger control plots (>20 acres)
- Apply in combination with other herbicides for resistance, efficacy, or cost management
- See other herbicide considerations to determine compatibility with current conditions
- 1 ppm endothall + 0.37 ppm diquat for rapid control in one week
- 1 ppm + 20 ppb bispyribac or penoxsulam
- Endothall before systemic herbicide to reduce biomass – or after to control skips
|
| Plant growth stage (target/non-target) |
- Need actively growing plants for herbicide uptake
- Best results for hydrilla control when applied in late winter / early spring
- Hydrilla is actively growing, most native plants may be dormant
- Less plant biomass and cooler water holds more oxygen to buffer plant decomposition
- Late season large-scale hydrilla control not recommended
- Mature hydrilla growth rate is slower; reduced herbicide uptake
- Plants have higher biomass and carbohydrate reserves; more difficult to control
|
| Plant susceptibility (target/non-target) |
- Effective season-long control of hydrilla and crested floating heart when applied early
- May also control non-target native submersed plants, especially:
- Coontail (Ceratophyllum demersum), southern naiad (Najas guadalupensis), Illinois pondweed (Potamogeton illinoensis)
|
| Potential for regrowth (target/non-target) |
- Hydrilla regrowth to water surface depends on extent of control, water clarity and depth
- Regrowth is slower if root crowns are killed – limited to tuber / turion sprouting
- Coontail, Southern naiad and Illinois pondweed are controlled by endothall
- Usually recover during the same or next growing season
|
| Climate Parameters | Management Considerations |
|---|
| Weather |
Daily
- Need at least 12-24 hours of exposure
- Dependent on dose and water temperature
- Windy conditions may increase dissipation in spot or band applications
Seasonally
- Less herbicide may be required in cooler months
- Microbial breakdown is slower so herbicide active for longer period
- Applying to actively growing plants increases uptake
- Increased uptake by actively growing plants in late winter / early spring
|
| Light intensity |
- No issues related to this tool – not broken down by photolysis
|
| Water temperature |
- Potassium endothall degradation can occur more rapidly in warmer water (>80°F)
- Could result in reduced efficacy
- Lower dissolved oxygen in water to buffer plant decomposition
- Algal growth may be more active to take up nutrients released by decomposing plants
|
