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.

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
  • 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
  • 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
  • No issues related to this tool
Livestock Consumption
  • No restrictions
Potable Water
  • No drinking water restrictions
  • No issues related to this tool
  • No fish consumption restriction
  • May temporarily accumulate in gills and liver – does not accumulate in muscle tissue
  • No issues related to this tool
  • 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
  • Not broken down by microbes
  • Adsorbs to organic materials and clay particles
  • Degree of adsorption depends on acidity and alkalinity
  • Not sensitive to photolysis
  • Not sensitive to hydrolysis
  • Does not disperse widely in treated waterbodies
    • Limited foliar spot applications, precipitation, settling, adsorption
  • Available in organic complex called copper chelate
    • Designed to keep in solution as long as possible
  • 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  
  • 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
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
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  
  • 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  
  • Not used to target native plants in FWC Programs
  • Copper is used for short-term algae control in ponds and drinking water reservoirs
  • Not used to target non-native plants in FWC Programs

  • 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


  • 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
  • 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
  • Controls only floating plants that are thoroughly wet with copper solution
  • 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
  • Apply via handgun from airboat tank mix or back pack sprayer for spot applications
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