Weeds

Article By:

Appleby, Arnold P. Crop Science, College of Agricultural Sciences, Oregon State University, Corvallis, Oregon.

Turner, Charles E. Agricultural Research Service, U.S. Department of Agriculture, Albany, California.

Last reviewed:November 2020

DOI:https://doi.org/10.1036/1097-8542.757403

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• Weeds, published June 2020:Download PDF Get Adobe Acrobat Reader

Unwanted plants, or plants whose negative values outweigh the positive values in a given situation. In general, weeds are useless plants (Fig. 1). They have low economic value or even negative value, especially when grown on cultivated land to the detriment of crops. Weeds adversely impact growers and farmers each year by reducing the yield and quality of their agricultural products. Especially in tropical areas, irrigation systems have become unusable because of clogging with weeds. Weeds can harbor deleterious disease organisms and insects that harm crops and livestock. In addition, weeds can cause allergic reactions and serious skin problems (for example, poison ivy rash), break up pavement, slow or stop water flow in municipal water supplies, interfere with power lines, cause fire hazards around buildings and along railroad tracks, and produce poisonous plant parts. See also: Agricultural science (plant); Agricultural soil and crop practices; Allergy

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