2,4-D Considerations
No single herbicide is appropriate for controlling all invasive aquatic plants (or nuisance growths of native aquatic plants), in all situations. A herbicide may perform differently depending on the waterbody, its use, the time of year—or even the time of day. Therefore, aquatic plant managers must have a thorough understanding of how each herbicide acts in Florida aquatic systems. The following parameters are evaluated when considering this herbicide to manage aquatic plants in a specific waterbody. Each parameter is linked to an explanation and examples are provided to demonstrate their relevance to developing comprehensive aquatic plant management strategies.
Table A: Herbicide Use Patterns for 2,4-D
– Widespread use of liquid formulations to control water hyacinth – used alone or in combination with diquat
– Occasional use of granular formulations for water lily control
Table B: Water Uses and Functions
| Water Use Parameters | Management Considerations |
|---|---|
| Downstream Uses and Needs | See irrigation |
| Fish and Wildlife Mgmt. | |
| Vegetation planting | Avoid applications within newly installed aquatic plant revegetation sites |
| Forage and prey | No issues related to this tool |
| Fisheries | No issues related to this tool used at rates for floating plant control in Florida waters |
| Non-game wildlife | No issues related to this tool |
| Endangered species | No issues related to this tool |
| Waterfowl | No issues related to this tool |
| Flood Control | No issues related to this tool |
| Navigation and Access | No issues related to this tool |
| Irrigation | Do not irrigate with treated water: If applied within 600 feet of functioning water intake Until 7 days after application within 600 feet of irrigation water intake, or An approved assay of water taken 3 days after application demonstrates a 2,4-D concentration of 0.1ppm or less |
| Livestock Consumption | 1 day water use restriction |
| Potable Water | Do not apply within 600 feet of a functioning potable water intake for floating plant control Coordinate applications with water facility operators |
| Recreation | |
| Boating | No issues related to this tool |
| Fishing | No fish consumption restriction |
| Hunting | No issues related to this tool |
| Swimming | No swimming restriction |
Table C: Herbicide, Waterbody, Plant, and Climate Parameters
| Herbicide Parameters | Management Considerations |
|---|---|
| Herbicide Rate | Generally applied at 0.5-1.0gpa Lower rates applied to younger more actively growing plants |
| Breakdown / Inactivation | Half life in water of approximately 7-14 days |
| Microbial | Broken down microbially – primary pathway Breakdown is rapid in organic soils |
| Adsorption |
Does not adsorb to organic or clay particles |
| Dissipation | Low dissipation when used at rates and use patterns applied to control water hyacinth in Florida Slightly soluble and rapidly taken up by plants Usually applied to small patches of water hyacinth |
| Formulation | |
| Liquid | Only the amine salt formulations are available in liquid formulation for use in Florida waters |
| Solid | Available in amine and ester formulations |
| Mode of Action | |
| Contact | Not a contact-type herbicide, but fast acting like contact for water hyacinth control Fast acting – rapidly absorbed by plant leaves, stems and roots Auxin hormone that translocates in the plant to the meristems Causes uncontrolled, unsustainable growth |
| Plant Growth Regulator | Classified as a plant growth regulator, but used as herbicide for aquatic plant control applications |
| Stewardship | |
| Herbicide resistance | No examples of resistance reported in Florida aquatic use patterns for water hyacinth control Rotate or use in combination with diquat where possible |
| Waterbody Parameters | Management Considerations |
| Hydrology | |
| Water depth | No issues related to this tool – used only for floating and emergent plant control |
| Water volume | No issues related to this tool – used only for floating and emergent plant control |
| Water movement | No issues related to this tool – used only for floating and emergent plant control |
| Water chemistry | |
| Dissolved oxygen (DO) | Use caution for larger applications to control plants in warm water to avoid DO sags Control small patches of water hyacinth even when oxygen is low to avoid subsequent large-scale problems |
| pH, alkalinity, hardness | No issues related to this tool |
| Nutrient content | Fast acting herbicide so may release nutrients from decomposing plants in large-scale control |
| Water transparency | No issues related to this tool |
| Sediment characteristics | |
| Composition | Sand/Clay – no issues related to this tool Organic – no issues related to this tool |
| Potential for resuspension | No issues related to this tool |
| Plant Physiology Parameters | Management Considerations |
| Plant origin/ growth potential | |
| Native | Frequently used in combination with diquat for frog’s-bit control Occasionally used for controlling floating or drifting mats of pennywort and smartweed Occasional control of water lilies with granular formulations |
| Non-native | Frequently used in combination with diquat for bur-head sedge control |
| Invasive | Frequently used for water hyacinth control |
| Plant growth stage (target/non-target) | Lower rates are applicable for young actively growing plants |
| Plant susceptibility (target/non-target) | Apply to actively growing target plants Good efficacy for water hyacinth control Control is relatively fast Water hyacinth usually grows among or immediately adjacent to beneficial native plants Non-target exposure is often unavoidable but impacts can be minimized 2,4-D does not control grasses – use 2,4-D rather than diquat when mixed with grasses Minimize non-target effects by altering dose, timing, or alternative herbicide 2,4-D is toxic to bulrush – use diquat to control water hyacinth mixed with bulrush Curls and browns spatter-dock leaves, but quickly recovers |
| Potential for regrowth (target/non-target) | Very effective for long-term control of water hyacinth Regrowth mostly from seeds and new plants Comingled non-target plants may be affected Use diquat to control water hyacinth growing among bulrush Spatter dock quickly recovers after |
| Climate Parameters | Management Considerations |
| Weather | Daily Highly volatile – do not apply in winds greater than 5 mph Use caution applying near crops like tomatoes, peppers, grapes that are extremely susceptible to 2,4-D Seasonally Several months of hydrilla control when applied in fall or winter Few months of control when applied to mature hydrilla in warm water |
| Light intensity | Low intensity reduces submersed plant ability to recover |
| Water temperature | Apply with water temperature generally 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 |
Table D: Other Parameters
| Parameter | Management Considerations |
|---|---|
| Cost | No generics available |
| Anticipated Control Amount | |
| Spatial | Acres Contact-type herbicide generally does not disperse outside treatment area Acres of submersed plants controlled generally equals acres of plants to which diquat (+Aquathol) is applied Percent of water column – need to treat entire water column |
| Duration | Provides good water hyacinth / water lettuce control – hydrilla control varies |
| Time to Achieve Control | Fairly fast acting for floating (few days) and submersed (several days) plant control |
| Contractor/Equipment | Apply by hand gun and airboat for small acreages of floating plants Apply aerially by helicopter for larger acreages of submersed plants Apply by hoses trailing from airboat for submersed plant control, especially small acreages of hydrilla (1-200 acres) |