Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/26/2013
Publication Date: 10/14/2013
Publication URL: http://handle.nal.usda.gov/10113/57996
Citation: Cooper, W.R., Spurgeon, D.W. 2013. Feeding injury to cotton caused by Lygus hesperus (Hemiptera: Miridae) nymphs and prereproductive adults. Environmental Entomology. 42(5):967-972. Interpretive Summary: The western tarnished plant bug (Lygus hesperus) is a pest of a wide-range of crops in the western United States. Researchers at USDA-ARS Shafter, CA, compared feeding behaviors, feeding injury to cotton, and within plant distributions among juvenile and pre-reproductive adult Lygus bugs. They found that fifth instars (the oldest nymphs before adulthood) caused more damage to cotton plants than did third instars (younger nymphs) or adults. The differences in feeding injury caused by Lygus of different ages could be explained by corresponding differences in within-plant distributions of the insects. Results from this study indicate that treatment thresholds that account for populations of Lygus nymphs would be more useful than thresholds based only on adult populations.
Technical Abstract: Despite numerous studies examining injury to cotton (Gossypium spp.) caused by different stages of Lygus hesperus Knight, no consistent trends are apparent. One explanation for inconsistencies among previous results is failure to account for important sources of biological variation. Because it was only recently recognized that feeding behavior and injury differed among adults of different physiological ages, this source of variance was not controlled in earlier studies of Lygus stage-dependent injury. We incorporated this knowledge into video assays and greenhouse experiments to compare feeding behaviors, within-plant distributions, and injury to cotton plants among L. hesperus nymphs and prereproductive adults. Laboratory behavior assays indicated third instars exhibited more stylet-probes, but of shorter duration, compared to prereproductive adults. Numbers and duration of stylet-probes by fifth instars were intermediate to those of third instars and adults. Total time spent stylet-probing was similar among the insect age-classes. On whole plants, third instars tended to reside within the bracts of squares (flower buds) greater than 3 mm in diameter, whereas fifth instars and adults tended to frequent the plant terminals. Adults were more likely than third or fifth instars to be located off the plants at any given observation. Plants exposed to fifth instars exhibited more square abscission and retained fewer squares 3-6-mm in diameter than did plants exposed to third instars or adults. Our results indicate that fifth instars are more injurious to cotton than third instars or prereproductive adults, and that differences in feeding injury correspond with within-plant distributions exhibited by different L. hesperus age-classes.