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Effect of Pigweed on Beet Armyworm Activity in Cotton

Stanley C. Carroll, Megha N. Parajulee, and Mark D. Arnold


Texas High Plains cotton losses due to beet armyworms, Spodoptera exigua (Hübner), have increased over the last ten years. This study was conducted in 2002 and 2003 to determine the influence of cotton planting date window (timely vs. late) and level of pigweed infestation (pigweed-infested vs. non-infested) on beet armyworm population abundance in Texas High Plains cotton. In both 2002 and 2003, planting date window did not influence seasonal differences in beet armyworm infestation. For both years, the presence or absence of pigweed contributed significantly to differences in seasonal beet armyworm activity in nearby cotton. In 2002, pigweed-infested cotton was observed to have a seasonal average of 3,240 larvae per acre compared with a significantly lower count of 1,015 larvae per acre in the clean-tilled non-infested cotton. Under lighter beet armyworm population levels in 2003, a seasonal average of 1,065 worms/acre was observed in pigweed-infested plots while only 195 worms/acre were detected in the plots without pigweed. The results of this study suggest that cotton fields infested with a preferred wild host, such as pigweed, have an increased risk for beet armyworm colonization.

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Document last modified 04/27/04