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Submitted to: Encyclopedia of Entomology
Publication Type: Book / Chapter Publication Acceptance Date: 4/9/2003 Publication Date: 4/30/2004 Citation: Showler, A.T. 2004. Weeds in crop systems for pest suppression. In: Capinera, J.L., editor. Encyclopedia of Entomology Volume 3. 1st edition. Hingham, MA: Kluwer Academic Publishers. p. 31-35. Interpretive Summary: Weed growth in cropping systems is generally considered to be deleterious to production and profit, but in some cases the vegetative diversity inherent to weedy agroecosystems supports higher numbers of prey arthropods that in turn support higher populations of natural enemies. Two cropping systems, sugarcane in Louisiana, and cotton in the Lower Rio Grande Valley of Texas, were described with regard to weed interactions with arthropod populations and effects on crop growth and yield. In the case of sugarcane, weed growth resulted in suppression of damage caused by the sugarcane borer because of higher populations of the imported fire ant. In the case of cotton, weed growth failed to suppress boll weevil damage to cotton squares because the most important boll weevil predator, the imported fire ant, was not encountered, and because the increases in natural enemy populations in weedy cotton habitats did not occur until after the cotton squares had become less vulnerable bolls. Technical Abstract: Weed growth in cropping systems is generally considered to be deleterious to production and profit, but in some cases the vegetative diversity inherent to weedy agroecosystems supports higher numbers of prey arthropods that in turn support higher populations of natural enemies. Those natural enemies can potentially suppress pest arthropods and injury to the crop. Principles of vegetational diversity, including polyculture, are summarized. Two cropping systems, sugarcane, Saccharum officinarum L., in Louisiana, and cotton, Gossypium hirsutum L., in the Lower Rio Grande Valley of Texas, were described with regard to weed interactions with arthropod populations and effects on crop growth and yield. The studies on Louisiana sugarcane showed that weedy sugarcane habitats harbored significantly more imported fire ant, Solenposis invicta Buren, populations that significantly suppressed damage to the crop caused by the sugarcane borer, Diatraea saccharalis (F.), the key pest. Although weed competition reduced stand density, profits in weedy habitats were increased because of low weed control inputs and because of the relatively low borer damage. In Texas cotton, weedy habitats were associated with significantly higher numbers of some arthropod predators than weed-free habitats. However, the numbers were higher near the end of the season after squares had become bolls that are less vulnerable to the key pest, the boll weevil, Anthonomus grandis grandis Boheman. |
