• Water-use restrictions depend on rate
  • 1-3 day restriction for ornamental plant watering
  • 1-5 day restriction for irrigating crops

• Avoid applications within newly installed aquatic revegetation sites

• Diquat dibromide has a low bioaccumulation potential

• Slight to moderate toxicity to fish
  • 8-hour LC₅₀ is 12.3 mg/L for rainbow trout and 28.5 mg/L for Chinook salmon
  • Do not use in waters used for fish protein concentrate or fish meal production

• No issues related to this tool

• No issues related to this tool

• Moderately toxic to birds
  • Mallard duck oral LD₅₀ is 564 mg/kg

• No issues related to this tool

• No issues related to this tool

• Water-use restrictions depend on rate
  • 1-3 day restriction for ornamental plant watering
  • 1-5 day restriction for irrigating crops

• 1-day water-use restriction if treated waterbody is the sole source for watering

• Rate-dependent setbacks of 350-1600 feet from functioning potable water intake
  • See label for specific information
  • Within these distances, shut off water intake for 1-3 days depending on rate, or
  • Until concentration falls below 0.02 ppm
• Coordinate with water facility manager for applications within 1600 feet of an active potable-water intake

• No issues related to this tool

• No fish consumption restriction
• Does not bioaccumulate in fish

• No issues related to this tool

• No swimming restriction

• Maximum label rate for controlling floating plants is 0.75 gpa
  • Generally applied at 0.25 to 0.5 gpa
• Applied at concentrations up to 0.37 ppm for submersed plant (hydrilla) control

• Almost immediately bound to soil or vegetation
• Tightly bound residues are not biologically available, so the herbicide is deactivated on soil
  • Bound residues are resistant to microbial degradation
  • Soil dissipation half-life exceeds 3 years

• Broken down slowly by microbes if not bound to sediments

• Binds tightly to clay and organic material
  • Do not apply in muddy or turbid waters for submersed plant control
  • Avoid tank mixing with muddy or turbid water before applying to emergent foliage

• Broken down slowly by sunlight if not bound to sediments

• Not sensitive to hydrolysis

• Dissipation half-life in water is 1-2 days as diquat is bound to sediment and deactivated

• Available in liquid formulation

• Not available in solid formulation

• Classified in WSSA Resistance Grouping #22
  • Photosystem I inhibitor

• Fast acting, contact-type herbicide: rapidly absorbed by plant leaves
• Interferes with cell respiration, the process by which plants take in oxygen
• Plant tissues are killed too quickly to allow translocation to other parts of the plant

• Used as herbicide for aquatic plant control applications in FWC programs
• Functions as growth inhibitor or growth regulator at lower rates

• Resistance confirmed in Landoltia species of duckweed in Florida
• Rotate or combine with other compounds where possible
  • Used in combination with endothall for submersed plant control
  • Combine with 2,4-D for mixed water hyacinth / water lettuce populations

• Avoid disturbing organic or clay sediments in shallow waters during submersed plant control (binds tightly and is inactivated in turbid waters)

• Use at rates up to 0.37 ppm for submersed plant control
• Amounts used are depth-dependent – see label for chart

• At least 24 hours of contact are required for submersed plant control

• Fast-acting when used in combination with endothall for submersed plant control
• Use caution in large-scale treatments in warm water to avoid dissolved oxygen depletion
• Treat only 1/3 to 1/2 of the water body at one time – wait 14 days between treatments

• No issues related to this tool

• Fast-acting contact type herbicide
• Nutrients may be released from decomposing plants in large-scale treatments

• Color/tannic content: no issues
• Turbidity: avoid mixing with, or applying to turbid waters
  • Binds tightly to clay and organic particles

• Sand: no issues related to this tool
• Clay: binds tightly to, and is inactivated in waters with suspended clay particles
• Organic: binds tightly to suspended organic particles and organic sediments

• Avoid stirring flocculent sediments during submersed plant applications
  • Especially in shallow water
• Avoid drawing clay or organic turbid water for tank mixes using diquat

• Illinois pondweed (Potamogeton illinoensis), southern naiad (Najas guadalupensis)
  • Occasionally controlled for access or navigation
  • 1.0 ppm potassium endothall + 0.37 ppm diquat

• Water fern (Salvinia minima)
  • Occasional control for access or navigation in confined areas
  • 0.5-0.75 gpa

• Hydrilla – where suspended organics or clay are not a concern
  • Poor or inconsistent control of hydrilla when used alone
  • 0.37 ppm diquat + 1 ppm potassium endothall (2 ppm endothall for mature hydrilla)
    • Rapid knockdown of hydrilla mat
    • Requires shorter retention time and faster control than endothall alone
    • Resistance management strategy
    • Cutting trails or small exposed bands
    • 0.37 ppm diquat + 0.10 ppm flumioxazin
  • Use in clear, low pH waters due to short flumioxazin half-life in pH > 7
  • Very active on water lilies
  • Resistance management strategy
• Floating plants (water hyacinth / water lettuce)
  • 1-2 qt/ac for smaller water hyacinth – up to 3 qt/ac for mature “Bull” hyacinth
    • Spray to wet – need complete coverage
  • 1-2 qt/ac for water lettuce
  • 1 qt diquat + 2 qt 2,4-D/ac for hyacinth/lettuce mix and resistance management
• Cuban club-rush and Wright’s nutrush
  • 2 qt/ac diquat or 1 qt diquat + 2 qt 2,4D/ac
• Giant salvinia (Salvinia molesta) and Feathered mosquitofern (Azolla pinnata)
  • 2 qt/ac

• Apply to actively growing target plants
  • Lower rates may be applicable for young, actively growing plants

• Resistance confirmed in Landoltia species of duckweed in Florida
• Good efficacy alone or combined with 2,4-D for water hyacinth/water lettuce control
• Use in place of 2,4-D to control water hyacinth mixed with bulrush (Schoenoplectus spp.)
  • Repeated use or higher doses of 2,4-D are toxic to bulrush
  • Diquat may spot or brown bulrush stems, but they quickly recover
• Controls some beneficial plants like southern naiad, Illinois pondweed, strapleaf sagittaria (Sagittaria kurziana) Spatter-dock (Nuphar spp.), jointed spikerush (Eleocharis interstincta)
• Minimize non-target effects by applying when native plants are dormant
  • Or before target plants mature or covers large areas

• Longer term control when applied to actively growing immature hydrilla
• Temporary injury reported for soft-stem bulrush in greenhouse studies

• Need at least 30 minutes of exposure for floating or emergent plants
• Need at least 24 hours of contact time for submersed plant control with endothall

Seasonally

• Several months of hydrilla control when applied in fall or winter
• 1-3 months of control when applied to mature hydrilla in warm water

• Low intensity may reduce submersed plant ability to recover after application

• Apply with water temperature above 50o F to ensure active growth of target plants
  • Plants must be actively growing for plant to take up herbicide
  • Do not apply for hydrilla control if strong thermocline exists
    • Or use deep and shallow trailing hoses to treat the entire water column

• Generics are available
• Alternate herbicides with equivalent efficacy may be available for some species

• Contact-type herbicide – generally does not disperse far outside submersed plant treatment area
  • Acres of submersed plants controlled equals area to which diquat (+ endothall) is applied
• Need to treat the entire water column

• Provides good water hyacinth/water lettuce control
  • Regrowth is generally from seed or new plants drifting from outside control zone
• Hydrilla control varies (1 to 6 months) based on water temperature and plant growth stage

• Fast-acting
  • Floating plant symptoms within hours after application – control in several days to one week
  • Submersed plant control in 1-2 weeks after application

• Apply by hand gun from airboat for small acreages of floating plants
• Apply aerially by helicopter for larger acreages of submersed plants
• Apply with endothall by trailing hoses from airboat for submersed-plant control, especially smaller acreages of hydrilla (1 to 200 acres)