Center For Aquatic And Invasive Plants

Glyphosate Considerations

*Important: See Reference Guide Beforehand

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.

These considerations are not meant to replace or contradict the EPA approved label.
Always read and follow the pesticide label for each product used.

Table A: Herbicide Use Patterns for Glyphosate

Target Plant	Scientific Name	Use Pattern	Compatible Herbicides
Torpedograss	Panicum repens	Frequent	Alone or with imazapyr
Cuban club-rush	Cyperus blepharoleptos	Frequent	Alone or with flumioxazin, Sometimes with 2,4-D
Paragrass	Urochloa mutica	Frequent	Usually used alone
Tussocks	Mixed floating masses of herbaceous plants – often mixed with woody plant species	Frequent	Alone or with imazapyr, Sometimes with diquat or 2,4-D
Tropical American Watergrass	Luziola subintegra	Frequent	Usually used alone
Floating plants	Water hyacinth or water hyacinth/water lettuce mix	Frequent	Alone or with 2,4-D
Cattail	Typha spp.	Frequent	Alone
Primrose willow	Ludwigia octovalvis / L. peruviana	Common	Alone or with flumioxazin, Sometimes with 2,4-D
West Indian marsh grass	Hymenachne amplexicaulis	Common	Alone or occasionally with 2,4-D
Spatter-dock	Nuphar advena	Occasional	Alone
Willows	Salix spp.	Occasional	Alone or with 2,4-D

Table B: Water Uses and Functions

Water Use Parameters	Management Considerations
Downstream Uses and Needs	Applications made to moving bodies of water must be made heading upstream Prevents concentrations of glyphosate in one area
Fish and Wildlife Mgmt.
Vegetation planting	Avoid applications within emergent aquatic plant revegetation sites, especially grass species
Forage and prey	No issues related to this tool
Fisheries	Acute Toxicity bluegill (96 hr LC₅₀) = 120 mg/L Acute LC₅₀ for rainbow trout > 2500 mg/L.
Non-game wildlife	Material is practically non-toxic to aquatic organisms on an acute basis LC₅₀ or EC₅₀ is > 100 mg/L in most sensitive species tested
Endangered species	No issues related to this tool
Waterfowl	Practically non-toxic to birds on an acute basis – LD₅₀ > 2,000 mg/kg Oral LD₅₀, Bobwhite quail > 3,800 mg/kg
Flood Control	No issues related to this tool
Navigation and Access	No issues related to this tool
Irrigation	No irrigation restrictions on the use of treated water
Livestock Consumption	No livestock watering restrictions
Potable Water	Do not apply within ½ mile upstream of a functioning potable water intake, or Within 1/2 mile of a functioning potable water intake in static water Coordinate applications with water facility operator Applications within 1/2 mile of potable water intake can be made if: The intake is shut down for 48 hours, or An approved laboratory analysis indicates the glyphosate concentration is below 0.7ppm
Recreation
Boating	No issues related to this tool
Fishing	No fish consumption restrictions
Hunting	No issues related to this tool
Swimming	No swimming restrictions

Table C: Herbicide, Waterbody, Plant, and Climate Parameters

Herbicide Parameters	Management Considerations
Herbicide Rate	0.5 mg/L – not applied to water; only to foliage of emergent vegetation Maximum 7.5 pt / ac
Breakdown / Inactivation	Half-life in ponds reported from 12-60 days
Microbial	Broken down microbially, primary pathway
Adsorption	Highly adsorbed on most soils, especially soils with high organic content
Photolysis	Minor breakdown pathway
Hydrolysis	Not sensitive to hydrolysis
Dissipation	Not active in water and will not kill submersed plants Binds tightly with soil so runoff is low
Formulation
Liquid	Available in liquid formulation only
Solid	Not available in solid formulation
Mechanism of Action	Classified in WSSA Resistance Grouping #9 Enzyme inhibitor – (Enolpyruvyl Shikimate-3-Phosphate (EPSP) Synthase Inhibitor)
Mode of Action
Systemic	Absorbed by foliar tissues only Moves to areas of new growth Prevents formation of essential aromatic amino acids in plants Without these essential amino acids, the plant cannot make proteins, enzymes, etc. Plant cannot continue growing and eventually starves and dies
Plant Growth Regulator	Not used as a plant growth regulator
Stewardship
Herbicide resistance	Resistance issues reported in terrestrial applications No examples of resistance reported in FL aquatic use patterns Rotate or use with another active ingredient where appropriate
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	Dissipation not an issue related to this tool Used only for floating and emergent plant control Applied directly to above-water leaves or stems
Water chemistry
Dissolved oxygen (DO)	Use caution for larger applications to control plants in warm water to avoid DO depletion
pH, alkalinity, hardness	No issues related to this tool
Nutrient content	No issues related to this tool
Water transparency	No issues related to this tool
Sediment characteristics
Composition	Sand/Clay – no issues related to this tool, applied only to leaves of floating or emergent plants Organic – no issues related to this tool, applied only to leaves of floating or emergent plants No pre-emergence or soil activity
Potential for re-suspension	Avoid disturbing sediments in shallow water if drawing for tank mixes
Plant Physiology Parameters	Management Considerations
Plant origin / growth potential
Native	Cattail, willow, tussocks Applied at 7.5 pt / ac Used for spot or large-scale control Rotational or combinational tool with imazamox, imazapyr, or 2,4-D Spatter-dock Applied at 7.5 pt /ac Used with tryclopyr and 2,4-D
Non-native	Primrose willow Applied at 7.5 pt /ac
Invasive	Torpedograss, Cuban club-rush, paragrass, tropical American watergrass, West Indian marsh grass Applied at 7.5 pt /ac alone or 6 pt + 2 pt imazapyr Floating plants (water hyacinth / water lettuce)
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 No activity on submersed plants Good efficacy for cattail and most grasses Control is relatively fast and long duration Not as effective controlling torpedograss in standing water Increase effectiveness by combining with imazapyr Minimize non-target effects by altering dose, timing, or use alternative herbicide Toxic to most grasses – avoid overspray onto desirable grasses
Potential for regrowth (target/non-target)	Very effective for long-term control for cattail and most grasses Avoid contact with comingled non-target plants, especially native grasses
Climate Parameters	Management Considerations
Weather	Daily Need at least six hours of contact for maximum effectiveness Avoid application in winds greater than 10 mph Seasonally Apply only to actively growing plants
Light intensity	No issues related to this tool
Water temperature	No issues related to this tool – not applied directly to water

Table D: Other Parameters

Parameter	Management Considerations
Cost	Generics available Alternative herbicides available for some plants controlled by glyphosate
Anticipated Control Amount
Spatial	Controls only emergent and floating plants to which it is applied No activity in submersed plants
Duration	Provides long term control for most grasses Torpedograss is an exception Glyphosate does not translocate well in plant tissues below the water surface
Time to Achieve Control	Yellowing symptoms in 2-3 days Control in 2-3 weeks Much longer for floating plants
Contractor/Equipment	Apply by hand gun and airboat for small acreages of floating and emergent plants Apply aerially by helicopter for larger acreages of cattail, torpedograss and Tropical American watergrass