Monday, June 27, 2011

Tarnished Plant Bugs Threatening Cotton Yields

Tim Reed, Extension Entomologist

June 21, 2011

Control measures for tarnished plant bugs (TPB’s) in the oldest cotton fields in north Alabama began two weeks ago and initial applications continue to be applied to later planted fields. Consultants report TPB pressure to be higher than normal than at this time last year and there is concern that some fields, especially older fields may require two TPB treatments. The cooler, wetter weather we are having this week in parts of Alabama will be favorable to TPB’s. The longer TPB treatments are postponed the more eggs are deposited by adult TPB’s which result in higher numbers of immature TPB’s present in late June and July. One consultant reports that TPB’s can presently be collected in a sweep net at any time of the day in north Alabama cotton fields but they tend to be more abundant on field edges. Some cotton fields in Montgomery county this week are also suffering 20% (Bt cotton threshold) or better pin head square loss due primarily to TPB damage and there could be control measures initiated in this central Alabama county this week. TPB’s are a much more serious pest for conventional cotton producers than for Bt cotton growers since all available chemicals that control adult plant bugs also significantly reduce beneficial insects/spiders. This increases the chances of a severe tobacco budworm infestation in the last half of June. Conventional cotton growers have a difficult time deciding on whether or not to spray for adult plant bugs in mid-June when they know it will be expensive to “fight” worms. Dry weather makes the decision even more difficult. Mississippi entomologists are reporting higher than normal numbers of tobacco budworm moths being collected in pheromone traps and budworm moths are now depositing low numbers of eggs on cotton in Montgomery county. Another concern for all cotton producers is the fear of spider mite populations increasing after TPB applications. Spider mites tend to appear in the same areas each year. Thus far a few north Alabama cotton fields have been treated with bifenthrin to help slow spider mites. Serious spider mite problems will require more expensive chemistry and consultants hope disease will take out the spider mites before more costly chemicals are required.