Center For Aquatic And Invasive Plants

Copper 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 Copper

Target Plant	Scientific Name	Use Pattern	Compatible Herbicides
Water hyacinth	Eichhornia crassipes	Spot applications	Used alone to control floating plants near potable water intakes
Water lettuce	Pistia stratiotes	Spot applications	Used alone to control floating plants near potable water intakes

Table B: Water Uses and Functions

Water Use Parameters	Management Considerations
Downstream Uses and Needs	Only used in Florida FWC-funded management program near potable water intakes Approved for use in potable waters Applied within setback areas where other aquatic registered herbicides cannot be used Spot applications for water hyacinth or water lettuce control Chelated copper compounds
Fish and Wildlife Mgmt.
Vegetation planting	Avoid applications within newly installed aquatic revegetation sites
Forage and prey	May be toxic to apple snails at higher application rates
Fisheries	May be toxic to some fish at higher rates, especially trout Fish toxicity generally decreases as water hardness increases
Non-game wildlife	No issues related to this tool
Endangered species	Discontinued use in areas accessible by manatees May be toxic to apple snails (primary food source of Everglades kite) at higher application rates
Waterfowl	Practically non-toxic to birds
Flood Control	No issues related to this tool – only applied in spot applications for floating plant control
Navigation and Access	No issues related to this tool
Irrigation	No issues related to this tool
Livestock Consumption	No restrictions
Potable Water	No drinking water restrictions
Recreation
Boating	No issues related to this tool
Fishing	No fish consumption restriction May temporarily accumulate in gills and liver – does not accumulate in muscle tissue
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	Applied at rates of 0.75-1.0 ppm for floating plant control near potable water intakes
Breakdown / Inactivation	As an element, copper can persist indefinitely Precipitates out of water within a few days Binds to particulates in water and sediments Accumulates over time
Microbial	Not broken down by microbes
Adsorption	Adsorbs to organic materials and clay particles Degree of adsorption depends on acidity and alkalinity
Photolysis	Not sensitive to photolysis
Hydrolysis	Not sensitive to hydrolysis
Dissipation	Does not disperse widely in treated waterbodies Limited foliar spot applications, precipitation, settling, adsorption
Formulation
Liquid	Available in organic complex called copper chelate Designed to keep in solution as long as possible
Solid	Copper sulfate available in crystal formulations; also called blue stone Copper chelate available in granulated or pelletized formulations
Mechanism of Action	Classified in WSSA Resistance Grouping as Unknown
Mode of Action
Contact	Absorbed by foliage or underwater tissues Does not move within the plant – contact type herbicide Appears to act on cell membranes or photosynthesis but how is unknown Cell membranes become leaky and cell contents spill out Without membranes, cells cannot make energy
Plant Growth Regulator	Used only as herbicide for aquatic plant control applications in FWC programs Functions as growth inhibitor or growth regulator at lower rates
Stewardship
Herbicide resistance	Resistance reported in blue-green algae after repeated use over decades in Minnesota Used occasionally for spot applications to floating plants in Florida
Waterbody Parameters	Management Considerations
Hydrology
Water depth	Not an issue with FWC use pattern of spot applications directly to foliage
Water volume	Not an issue with FWC use pattern of spot applications directly to foliage
Water movement	Not an issue with FWC use pattern of spot applications directly to foliage
Water chemistry
Dissolved oxygen (DO)	Not an issue with FWC use pattern of spot applications directly to foliage May be an issue for large-scale algae control in potable water reservoirs
pH, alkalinity, hardness	In waters of < 50ppm alkalinity, may be toxic to fish at rates applied to control plants Copper sulfate precipitates in waters with high alkalinity (> 250 ppm) Copper precipitation less of a concern with chelated copper formulations
Nutrient content	Fast acting, but generally not an issue with the small-scale use patterns in Florida
Water transparency	Color/tannic content – no issues Turbidity – avoid applications to highly turbid waters
Sediment characteristics
Composition	Sand/Clay – adsorption to organic particulates and clay sediments Organic – adsorption to suspended organic particles Avoid applying pellets to deep flocculent organic sediments
Potential for re-suspension	Avoid disturbing sediments when applying to shallow waters
Plant Physiology Parameters	Management Considerations
Plant origin / growth potential
Native	Not used to target native plants in FWC Programs Copper is used for short-term algae control in ponds and drinking water reservoirs
Non-native	Not used to target non-native plants in FWC Programs
Invasive	Water hyacinth and water lettuce Foliar application at .75 – 1.0 ppm Occasionally used near potable water intakes where other herbicides are restricted
Plant growth stage (target/non-target)	Need actively growing plants for herbicide uptake For best results, apply to young, actively growing plants
Plant susceptibility (target/non-target)	Current use in Florida is for floating plant control near potable water intakes More effective on young and actively growing floating plants
Potential for regrowth (target/non-target)	Requires thorough wetting with spray solution Reinspect within 1-2 weeks for plants that may have been missed
Climate Parameters	Management Considerations
Weather	Daily Apply when rain is not forecast Seasonally Apply to actively growing plants
Light intensity	Not broken down by photolysis Higher light intensity may equate to rapid plant growth and herbicide uptake
Water temperature	No issues related to this tool

Table D: Other Parameters

Parameter	Management Considerations
Cost	Herbicides with equivalent floating plant control efficacy are available Only used in FWC program near potable water intakes where other herbicides are restricted
Anticipated Control Amount
Spatial	Controls only floating plants that are thoroughly wet with copper solution
Duration	Provides long-term control of floating plants Better efficacy with young / small / actively growing floating plants
Time to Achieve Control	Controls floating plants in 2-3 days after application
Contractor/Equipment	Apply via handgun from airboat tank mix or back pack sprayer for spot applications