General Information


Harpoon Granular is a chelated copper formulation that effectively controls Hydrilla, Egeria (Brazilian Elodea), Naiads, Coontail, Elodea, Water Lettuce, Water Hyacinth, Giant Salvinia, and other species having a sensitivity to copper absorption. In waters with low alkalinity (hardness), Harpoon may also control Eurasian Watermilfoil and Horned, Sago, American, Curly-leaf, & Floating-leaf Pondweeds. Harpoon Granular may be applied to slow moving or quiescent bodies of water, including lakes, fish hatcheries, potable water reservoirs, golf courses, and ornamental, fish and fire ponds.

Limitations, Restrictions, and Exceptions

HERBICIDE APPLICATION Quiescent or Slow Moving Water

A. LARGE AREA TREATMENT (over 5,000 sq. ft.)

1. Identify form(s) of targeted submersed aquatic plants.

2. Estimate the targeted Plant Growth Height (in ft.) in the water column. This would be the distance from the base to the top of plants.

3. To calculate surface area (acres) of the treatment area (area of infestation), refer in the label for the formula.

4. Refer to Table 1 to determine lbs. of Harpoon Granular to apply per Surface Acre based upon Plant Growth Height.

5. Distribute Harpoon Granular evenly over the water surface directly over the targeted vegetation, adjusting rates based upon the height of the vegetation in the water column. A dry fertilizer spreader or blower may be used to ensure even distribution.

Select low range rate for Light to Moderate Growth and upper range rate for heavy infestations. Light to Moderate Growth is defined as a treatment area where submersed plants have not reached the water surface (“topped out”) and less than 65% of the bottom or water surface (in the case of floating plants) is covered with target plants. Heavy Infestations are areas where submersed vegetation growth has reached the water surface and/or bottom growth cover more than 65% of the treatment area. Do not apply more than 1.0 ppm copper.


Do not apply this product in a way that will contact workers or other persons, either directly or through drift.

Only protected handlers may be in the area during application. For any requirements specific to your State or Tribe, consult the State or Tribal agency responsible for pesticide regulation.

Do not apply this product in a way that will contact adults, children, or pets, either directly or through drift.

Some states may require permits for the application of this product to public waters. Check with your local authorities.

(For all sizes) Do not enter or allow others to enter until application of product has been completed in the area.


Injury may occur if concentrated Harpoon granules or treated water concentrations above 1.0 ppm of copper comes in contact with ornamentals, crops, grass, or other foliage. Do not exceed 1.0 ppm total copper in treated water.


- Confirm that target plants are either listed on the label or related to the listing provided. Not all aquatic plants are sensitive to Harpoon Granular.

- It may be necessary to test water hardness if there are trout. Minimum water hardness is 50 ppm.

- Apply early in the day under calm, sunny conditions. Harpoon Granular works best when water temperatures are at least 60°F.

- Treat when and where growth first begins to appear or create a nuisance.

- Apply in a manner that will ensure even distribution of the chemical within the treatment area.

- Re-treat areas if re-growth begins to appear and seasonal control is desired. Allow one to two weeks between consecutive treatments.

- Allow seven to ten days to observe the effects of treatment (bleaching and breaking apart of plant material).

- Under conditions of heavy infestation, treat only ? to ½ of the water body at a time to avoid fish suffocation caused by oxygen depletion from decaying algae.

- Algae growth on and around target plants may interfere with the uptake of Harpoon Granular. Pre-treat these areas with Cutrine-Plus algaecide. Do not exceed 1.0 ppm of total copper when using Harpoon Granular in combination with copper-based algaecides.