• Do not apply within 600 feet of a functioning potable water intake

• Spotting may occur on comingled emergent plants from liquid aerial applications

• No issues related to this tool – does not bioaccumulate

• Practically non-toxic to fish
  • Blue gill EC₅₀ = 1,071 ppm
  • Rainbow trout EC₅₀ = 363 ppm

• No issues related to this tool

• No issues related to this tool

• Non-toxic to waterfowl – mallard duck LD₅₀ = 328 mg/kg (ppm)

• No issues related to this tool

• No issues related to this tool

• No irrigation restrictions

• No issues related to this tool for applications in Florida public waters

• Apply 600 feet or greater from a functioning potable water intake
• Applications within 600 feet of potable water intake can be made if:
  • The intake is shut down until approved laboratory analysis indicates endothall below 0.1 ppm
  • Coordinate applications with water facility operator

• No issues related to this tool

• No fish consumption restriction – does not bioaccumulate in fish

• No issues related to this tool

• No swimming restriction

• 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

• Half-life is generally 3-7 days

• Primary degradation pathway
  • Degradation rate is water-temperature and plant density dependent

• Does not adsorb to suspended solids or sediments

• Does not degrade by photolysis

• Not sensitive to hydrolysis

• 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)

• Available in liquid formulation
• Can be used as surface or sub-surface application
  • Achieves uniform concentration throughout water column within a few hours

• 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

• Unclassified in WSSA Resistance Grouping
  • Protein phosphatase inhibitor

• 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

• Not used as a plant growth regulator in Florida aquatic plant control applications

• 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

• Important to know water depth to calculate appropriate dose
• Potassium endothall is used to dose water column for submersed plant control

• Accurate bathymetry is essential to calculate appropriate concentration
• See label chart when applying for submersed plant control

• 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

• Caution when controlling large, dense hydrilla stands in warm water to avoid DO depletion
  • Particularly when combined with diquat

• No issues related to this tool

• Relatively fast-acting herbicide
• Hydrilla mats generally decline in 1-3 weeks after application
• Nutrients may be released from decomposing plants in large treatments

• 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

• Sand / Clay – no issues related to this tool
• Organic – no issues related to this tool, does not adhere to organic material

• No issues related to this tool, does not adhere to organic material

• Occasionally applied to control some native submersed plants at 3-5 ppm
  • Coontail (Ceratophyllum demersum), southern naiad (Najas guadalupensis), Illinois pondweed (Potamogeton illinoensis)

• Little to no control reported with this compound for non-native plant management in Florida

• 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

• 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

• 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)

• 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

• 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

• No issues related to this tool – not broken down by photolysis

• 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

• No generics or equivalent modes of action available

• Area of hydrilla control is similar to area to which endothall is directly applied
• Some dissipation and control may result outside of application zone
• Does not disperse as widely as herbicides with longer half-lives such as fluridone or penoxsulam
  • Managers exploit dissipation by applying potassium endothall in bands up to 200 feet apart
    • Herbicide blends within a few hours of application to dose entire area between bands

• Control duration depends on initial dose and length of exposure, extent of control and water clarity
  • If root crowns are killed, regrowth is slower; from tubers, seeds, or fragments
  • Recovery is slower in tannic, turbid or deep water where light is less intense

• Symptoms in 7-10 days and control in 2-3 weeks

• Surface or sub-surface application by boat / airboat for small / moderate scale hydrilla control
  • Additional boats needed for large-scale control to achieve / sustain dose in entire control zone
• Apply aerially by helicopter for larger acreages