How to Kill Plants with Copper

Copper is a trace element needed for proper development and function in plants. A lack of or an overabundance of the element can kill plants. Because of the ongoing negative effects of high levels of copper in soils, if copper must be used to destroy plants, consider creating a deficiency rather than a toxic level to do the job. Signs of copper toxicity often mimic signs of copper deficiency. Plant foliage may develop a red, brown, blue-green or yellow coloration. Plants may become stunted, and their roots may develop poorly. Their leaves may show signs of drying, chlorosis or wilt. This damage renders the plant more sensitive to frost damage. Copper levels of 150 ppm or greater in plant tissues can cause plant toxicity.

Things You'll Need

• Nitrogen fertilizer, manure, ammonium nitrate, urea, aluminum sulfate or sulfur
• Clay soil
• Copper sulfate

Instructions

1. Create a high level of copper in the soil around the plant to cause toxicity. High levels of copper disrupt photosynthesis in plants. According to the Cooperative Extension System, large doses, high temperatures and acidic soil conditions increase the effects of copper on plants.

2. Stop making corrections to the soil pH if any are being applied, or attempt to lower the pH of the soil to create an acidic soil environment to make copper more effective at killing the plants. Add nitrogen fertilizer, manure, ammonium nitrate, urea, aluminum sulfate or sulfur. Work one or more of these into the soil in enough quantity to create an acidic soil.

3. Introduce clay soil around the plants if they are located in sandy soil. Clay soils and soils rich in minerals help hold on to copper, while copper leaches more easily from sandy soils.

4. Apply an available form of copper, such as copper sulfate. Such products are readily available, as they are usually used to treat fungal and bacterial diseases in crops.

Tips & Warnings

• Copper does not degrade in the soil, and copper applications can lead to copper accumulation in soils, according to the Cooperative Extension System. Once copper accumulation becomes a problem in the soil, it is practically impossible to reverse.

• Copper binds to the soil. It affects the availability of nitrogen in the soil and can lead to reduced soil fertility, warns the Penn State College of Agricultural Sciences. It can kill beneficial bacteria and microorganisms necessary to good soil health. Copper runoff poses a danger to fish. High dosage exposure and repeated exposures can cause a range of negative effects on the human body.

References

• Cooperative Extension System; Organic Management of Late Blight of Potato and Tomato With Copper Products; Alex Stone, et al.; March 2010
• University of Minnesota Extension; Copper for Crop Production; George Rehm, et al.; July 2009
• Michigan State University Extension; Copper; M.L. Vitosh, et al.; July 1997
• Penn State College of Agricultural Sciences; Copper Sulfate Hoof Baths and Copper Toxicity in Soil; Rick Stehouwer, et al.; March 2004
• Extoxnet Cooperative Extension Offices of Cornell University, et al.; Copper Sulfate; May 1994
• University of Minnesota Extension; Herbicide and Nonherbicide Injury Symptoms on Spring Wheat and Barley: Nutrient Deficiencies; 2009

Resources

• Press Republican/Cornell Coop. Extension; Manage Nuisance Plants in Your Yard...; Amy Ivy; May 2010
• Clemson Cooperative Extension; Changing the pH of Your Soil; Marjan Kluepfel, et al.; June 1999
• Penn State Cooperative Extension; Soil Acidity and Aglime; Douglas B. Beegle; 1995