| Herbicide Rate | - 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 hyrilla control
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| Breakdown / Inactivation | Less than 48 hours half life in water reported |
| Adsorption | Binds tightly to clay: do not use in muddy or turbid waters for submersed plant control |
| Microbial | Broken down microbially |
| Photolysis | Broken down by sunlight |
| Dissipation | Highly soluble, but rapidly taken up by plants or adsorbed to clay and organic particles, so dissipation is slow |
| Formulation | |
| Liquid | Available in liquid formulations only |
Mode of Action
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| Contact | Fast acting, contact-type herbicide: rapidly absorbed by plant leaves. Interferes with plant cell respiration |
| Systemic | Little to none: injures plants too rapidly to be translocated within plant tissues |
| Plant Growth Regulator | Not used as a plant growth regulator |
| Stewardship | |
| Herbicide resistance | - Resistance confirmed in some species of duckweed in Florida
- Rotate other compounds where possible
- Used alone for most floating plant applications. Therefore, consider rotating with other herbicides
- Used in combination with endothall or occasionally copper compounds for submersed plant control
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| Microbial degradation | Taken up rapidly by plants and broken down slowly by microbes. Repeated use does not affect enhanced microbial degradation. |
| Waterbody Parameters | Management Considerations |
| Hydrology | |
Water depth
| Avoid disturbing organic or clay sediments in shallow waters during submersed plant control (binds tightly and is inactivated in turbid waters) |
| Water volume | - Use at rates up to 0.37 ppm for submersed plant control
- Amounts used are depth-dependent. See label for chart.
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| Water movement | At least 24 hours of contact are required for submersed plant control |
| Water chemistry | |
| Dissolved oxygen (DO) | - Fast-acting when used in combination with endothall or copper for submersed plant control
- Use caution in large-scale treatments in warm water to avoid dissolved oxygen depletion
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| Alkalinity, ph, hardness | No issues |
Nutrient content
| Fast-acting herbicide. Nutrients may be released from decomposing plants in large-scale treatments. |
| Water transparency | - Color/tannic content: no issues
- Turbidity: avoid mixing with, or applying to, turbid waters. Binds tightly to clay and organic particles.
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| Sediment characteristics | |
Composition
| - Sand/clay: binds tightly to, and is inactivated in waters with suspended clay particles
- Organic: binds tightly to suspended organic particles
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| Potential impacts from sediment resuspension | - Avoid stirring flocculent sediments during submersed plant applications, especially in shallow water
- Avoid drawing turbid water for tank mixes using diquat
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| Plant Physiology Parameters | Management Considerations |
| Plant origin/ growth potential | |
| Native | - Frequent use for water lettuce and water meal control: infrequent for cattail control
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| Non-native | - Frequent use for salvinia control
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| Invasive | - Frequent use for water lettuce and water hyacinth control
- Occasional use for small-scale or spot hydrilla control
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| Plant growth stage (target/non-target) | Lower rates may be applicable for young, actively growing plants |
Plant susceptibility (target/non-target)
| - Apply to actively growing target plants: resistance confirmed in some duckweed species. Good efficacy for water hyacinth/water lettuce control.
- Used alone or in combination with 2,4-D to control water hyacinth mixed with water lettuce
- Used in place of 2,4-D to control water hyacinth when mixed with bulrush (Scirpus spp.)
- Bulrush provides valuable cover and substrate for fisheries: the seeds are used by waterfowl
- Repeated use or higher doses of 2,4-D are toxic to bulrush
- Diquat may spot or brown bulrush stems, but they quickly recover
- Poor or inconsistent control of hydrilla when used alone
- Used in combination with copper herbicides to eradicate new patches of hydrilla, especially at boat ramps
- Used in combination with endothall to control small to moderate areas of hydrilla in quiescent waters
- Diquat rates of 0.37 ppm; endothall rates of 1 to 3 ppm
- Control is relatively fast
- Faster than with endothall alone
- Hydrilla mats begin to collapse in as little as 24 hours
- Controls some beneficial submersed plants like southern naiad, Illinois pondweed, and strapleaf sagittaria
- Minimize non-target effects by applying when native plants are dormant or before hydrilla covers large areas
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| Potential for regrowth (target/non-target) | - Very effective for long-term control of water hyacinth and water lettuce
- Regrowth is mostly from seeds and new plants flushed into the area
- Hydrilla control varies with season and plant growth stage
- Regrowth from turions, tubers, and surviving root crowns: generally 3 to 6 months
- Commingled non-target plants may be spotted or browned during floating plant control, but usually recover
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| Climate Parameters | Management Considerations |
| Weather | - Daily
- Need at least 30 minutes of contact for floating or emergent plants
- Seasonal
- Several months of hydrilla control when applied in fall or winter
- 1 to 3 months of control when applied to mature hydrilla in warm water
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| Light intensity | Low intensity reduces submersed-plant ability to recover |
| Water temperature | - Apply with water temperature generally above 50oF 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
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