Native plants have an advantage over non-native or ornamental species in that their adaptations to the environment lower their risk for pest invasions. Herbicides are a last resort when other methods such as manual removal of weeds prove ineffective. When choosing an herbicide, select a pesticide which is selective. Selective herbicides target specific plants, making them a safer alternative to broad spectrum pesticides. Proper selection of an herbicide depends upon correct identification of the pest. Your agricultural state extension office can provide assistance.
Chemicals
Chemicals such as copper sulfate are effective herbicides for reducing algae populations. Algae can shade the surface of the water, making it difficult for submerged native plants to survive. Copper sulfate is an affordable herbicide which will control most types of algae, explains the Illinois Department of Natural Resources. A solution mixed with citric acid will increase its effectiveness.
Liquid Applications
One environmental risk of using herbicides is drift to non-targeted species. In order to minimize the impact on native flowers, you can apply pesticides to the cut stumps or directly to the bark of invading woody vegetation with a brush or sponge. This method allows you to specifically target the weeds without damaging native flower populations. Because of the potential toxicity, wear rubber gloves when applying herbicides.
Allelopathic Plants
Although they are not what you might think of as herbicides, allelopathic plants use their own defensive system to maintain their populations. Some plants such as black walnut trees release chemicals into the surrounding soil which will control competing species. Other allelopathic plants include American sycamore, red oak and American elm. Using allelopathic plants for weed control is not a new practice. A 1983 study in the "Journal of Chemical Ecology" found that sunflower effectively controlled weeds.
Hot Water
A simple yet effective solution for treating weeds is to douse them with hot water, recommends Avian Web. You can target specific plants while minimizing the environmental impact of chemical herbicides. To increase its weed-killing power, add 1 ounce of 3 percent hydrogen peroxide to 1 quart of hot water. These methods are most effective when you can apply the water or the solution directly onto the weeds.
Vinegar
Vinegar has gained popularity as an environmentally friendly solution to weeds. The U.S. Department of Agriculture found that a 5- to 10-percent vinegar solution proved an effective herbicide for emerging weeds. While it is earth-friendly, careful application is necessary to avoid spray reaching your native flowers. To minimize drift, apply the herbicide on non-windy days in the morning.
References
- "Illinois Pesticide Applicator Training Manual: General Standards"; P. Nixon et al; 1995
- "Aquatic Plants: Their Identification and Management"; Illinois Department of Natural Resources; 1997
- "Invasive Plants: Weeds of the Global Garden"; John M. Randall and Janet Marinelli (eds.); 1996
- "Journal of Chemical Ecology"; Weed Control Using Allelopathic Crop Plants; G. Leather; August 1983
- Avian Web LLC: Safe Alternatives for Weed Control, Pesticides / Insecticides
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