Cotton Pests - Boll Weevil |
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Background
Biology
The boll weevil, Anthonomus grandis Boheman, is a small, hard-shelled snout beetle averaging ¼-inch in length. It has a yellowish, grayish, or brownish color and becomes nearly black with age. The boll weevil belongs to the Curculionidae, a family of insects that is strictly phytophagous (plant eating). This group has a high degree of host specificity (a trait referring to insects that can live and feed on only a limited number of plant species) and generally prefers flower buds for feeding and reproducing.
Boll weevils overwinter as adults sheltered beneath brush and forest litter and in other protected locations in and around cotton fields. Adults that survive the winter emerge from overwintering sites in the spring and begin feeding on the tips of cotton seedlings and cotton flower buds (called squares). The female boll weevil deposits eggs in the cotton squares, and, later in the season, in the soft cotton bolls. Eggs are deposited singly at the bottom of cavities or punctures made in the squares and bolls. The larvae feed for 7 to 14 days and pupate. After 3 to 5 days, the adults emerge.
After mating, females in the new generation begin laying eggs in 3 to 5 days. An average of five generations occur in a single growing season, although as many as 10 generations may develop under favorable conditions.
Squares that are infested with boll weevils typically fall off the cotton plant. Bolls infested with boll weevils typically remain on the plant, but they either fail to produce cotton lint or produce an inferior quality or smaller quantity of lint.
Depending on the severity of winter temperatures, as many as 10 to 60 percent of boll weevil populations may survive the winter. Very cold winter temperatures, or very hot and dry summer conditions, can have an impact on weevil numbers the following year.
Images
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| Adult boll weevil on cotton. Image: Clemson University - USDA Cooperative Extension Slide Series |
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| Adult boll weevil on cotton. Image: Clemson University - USDA Cooperative Extension Slide Series |
Illustration - Boll Weevil Life Cycle
Host
Cotton
Distribution
By the early 1980’s, the boll weevil had infested nearly all cotton grown in the U.S., including about 15 million acres in 17 states from California to Virginia and north to Kansas. The only weevil-free areas prior to the eradication program were in the San Joaquin Valley of California and the High Plains of West Texas. Since sequential eradication began in 1983, the infestations have gradually been eliminated, so that by the spring of 2009 about 94 percent of all cotton acreage in the U.S. had become weevil-free.
Chronology of the pest in the United States
The boll weevil, a native of Mexico and Central America, was first introduced into the United States near Brownsville, Texas, about 1892. By 1922, the pest had spread into cotton-growing areas of the United States from the eastern two-thirds of Texas and Oklahoma to the Atlantic Ocean. Northern and western portions of Texas were colonized by the boll weevil between 1953 and 1966, and the desert Southwest areas of Arizona and Southern California were infested in the early 1980’s. The eradication program, involving a series of progressive expansions across more than 40 production zones in 17 states, began in North Carolina in 1983.
Technical Working Group
Beltwide Technical Advisory Committee (serves as part of the National Cotton Council’s Boll Weevil Action Committee).
Research
Limited research is being conducted as the program moves toward completion, including work on weevil resistance, pheromone release rates on extended lure, and the ability to identify the origin of reintroduced weevils.