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Title: EARLY-SEASON COLONIZATION PATTERNS OF THE BOLL WEEVIL (COLEOPTERA: CURCULIONIDAE) IN CENTRAL TEXAS COTTON

Author
item Reardon, Brendon
item Spurgeon, Dale

Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/11/2002
Publication Date: 4/1/2003
Citation: REARDON, B., SPURGEON, D.W. EARLY-SEASON COLONIZATION PATTERNS OF THE BOLL WEEVIL (COLEOPTERA: CURCULIONIDAE) IN CENTRAL TEXAS COTTON. JOURNAL OF ECONOMIC ENTOMOLOGY. 2003. 96(2):328-333.

Interpretive Summary: It is commonly believed that boll weevils entering cotton in the spring are located mainly near the edges of the fields. However, evidence to substantiate this belief is not available in the published literature. We collected adult weevils and infested flower buds (squares) from cotton fields in Central Texas, arranging samples in a pattern designed to show if weevils were unequally distributed among the outside 70 rows of each field. Samples were collected from the time plants were 4-6 inches in height until the cotton began to flower. We could show no differences in the numbers of male or female weevils, or in the numbers of weevils collected between years or among different stages of cotton plants. Although our results suggested the chances of capturing a weevil or finding an infested square decreased slightly with increased distance from the field edge, we could not demonstrate differences in numbers of weevils that were related to locations of the samples. Thus, we did not find that most weevils are located on field edges. These results indicate that early-season sprays applied only to field edges should not be expected to provide effective control of boll weevil populations.

Technical Abstract: It is commonly believed that colonization of early-season cotton, Gossypium hirsutum L., by overwintered boll weevils, Anthonomus grandis Boheman, is concentrated on field margins. However, supporting experimental evidence is not available. In 1999 and 2000, we examined colonization patterns of overwintered boll weevils in Central Texas cotton on the bases of adult collections by a pneumatic sampler and hand collections of abscised infested squares. Samples were taken from sites arranged in a grid that extended inward >70 m from the field margin. Adults were collected from shortly after seedling emergence until the flowering stage, and infested squares were collected during the one-third grown square stage. Despite numerical trends, the numbers of adult weevils collected were not significantly different between years or sexes, or among plant phenological stages. Field-to-field variation among collections was considerable and likely prevented detection of differences among these factors. Spatial patterns represented by adult weevil and infested square collections were examined by logistic regressions fitted to the respective probabilities of weevil detection at each designated sample site. Although we observed trends for slightly decreased probability of weevil detection with increased distance from the field margin, these trends were too weak to be demonstrated statistically. Our results indicate the boll weevil does not consistently exhibit a strong edge-oriented colonization pattern, and that management tactics that are predicated on these patterns, such as border sprays, should be used with caution.