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Impact of the Boll Weevil Eradication Program on Beneficial Insects in Cotton: Is there a Canary in the Coal Mine

Allen Knutson, James Butler, and Julio Bernal


Densities of predatory insects and spiders were sampled in cotton fields under boll weevil eradication and outside of eradication for two growing seasons in Central Texas to determine if sampling could anticipate an increasing risk of outbreaks of secondary pests, primarily beet armyworm and bollworm/budworms. As expected, densities of most predatory insects and spiders were significantly lower under eradication. An exception was lady beetles which were significantly more abundant under eradication due to the greater density of cotton aphids. Densities of fire ants and immature pirate bugs (Orius species) were much lower under eradication relative to densities in fields outside of the eradication program and thus were too sensitive to malathion to be useful indicators. Spiders increased early in the season, but then began to decline as fields were repeatedly treated with malathion. In contrast, spider densities continued to increase throughout the season in fields not under boll weevil eradication. Total spider densities were negatively correlated with densities of beet armyworms and bollworms. Results suggest that spiders may be a useful indicator group for assessing the risk of outbreaks of caterpillar pests in a boll weevil eradication program. Also, spiders are easily and quickly sampled using the beat bucket method and are easily identified in the field.

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Document last modified 04/27/04