Feeding injury to cotton caused by Lygus hesperus (Hemiptera: Miridae) adults of different reproductive states

Authors: Cooper, William - Rodney; Spurgeon, Dale

Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/7/2011
Publication Date: 4/25/2011
Citation: Cooper, W.R., Spurgeon, D.W. 2011. Feeding injury to cotton caused by Lygus hesperus (Hemiptera: Miridae) adults of different reproductive states. National Cotton Council, Memphis, TN. pp. 1215-1218.

Interpretive Summary: The western tarnished plant bug is a key cotton pest in the western United States. Feeding by plant bugs injures flower buds (squares) and causes them to drop from the plant. In recent studies, we determined that feeding behavior differs between pre-reproductive adults and reproductive adults. In those studies, pre-reproductive adults fed more than did mated or unmated eproductive adults. We compared the feeding injury to cotton squares caused by adults that were pre-reproductive, reproductive and unmated, and reproductive and mated. Within a greenhouse, cotton plants were caged for one week with male or female plant bugs of different reproductive states. Feeding injury was assessed by counting the number of dropped squares and by searching squares for injury caused by plant bug feeding. Pre-reproductive adults caused significantly more squares to drop and more square injury than did either mated or unmated reproductive adults. Overall, pre-reproductive adults caused three times more feeding injury than did reproductive adults. These results are consistent with our previous feeding behavior studies, and demonstrate that adult reproductive state is a source of variation that must be controlled in future studies involving plant bugs. This information will help efforts to develop a better understanding of the damage caused by plant bugs.

Technical Abstract: Lygus hesperus Knight is a key pest of cotton (Gossypium spp.) in the western United States. Lygus-induced injury is considered to be highly variable, and no clear relationship between Lygus population level and plant injury has been established. A likely explanation for this variability is failure to account for important sources of biological variation among experimental insects. Recent video-based laboratory studies indicated that feeding behaviors and trivial movements differed among classes of adult Lygus of different gender and reproductive state (pre-reproductive, reproductive and unmated, and reproductive and mated). Therefore, we assessed the feeding injury to greenhouse-grown cotton plants caused by L. hesperus adults of different gender and reproductive states. Cotton plants were grown in single rows within 680-l planters (blocks) to the ‘match-head’ square stage. The experimental design was an incomplete block with gender assigned to blocks and reproductive state assigned to plants within blocks. Individual plants, enclosed within acrylic cages with nylon mesh windows, were each infested with one adult L. hesperus. Insects were removed from the cages after 1 wk. Feeding injury was evaluated by counting the numbers of missing squares and squares with injured anthers. Pre-reproductive adults caused significantly more square abscission and square injury than did reproductive adults, but feeding injury did not differ by mating status or gender. These results are consistent with results of our previous video-based assays, and indicate adult reproductive state represents a source of variation that must be controlled in studies to evaluate Lygus-induced injury to cotton.