Examining the dispersal capabilities of Lygus hesperus and its natural enemies in California's San Joaquin Valley

In order to manage the western tarnished plant bug (Lygus hesperus Knight) from a landscape perspective, it is essential to understand its dispersal capability. In this study we measured the dispersal of Lygus hesperus and its natural enemies from a cut alfalfa field into adjacent cotton fields. This modified mark-release-recapture experiment marked an existing insect community in a commercial alfalfa field and then monitored movement after the monthly cutting of alfalfa for hay. In this experiment we marked a 12-acre portion of a flowering alfalfa field that had a substantial density of Lygus hesperus (average of 20 Lygus per 50 sweeps) with two distinctive protein marks (diluted cow’s milk and egg whites). After the grower cut the alfalfa field, cotton fields to the west, northwest, and southeast of the cut alfalfa field were sampled two, four, and six days after the cutting. In addition to Lygus hesperus, predators including Geocoris spp., Chrysoperla carnea, and Hippodamia convergens, and were collected. Understanding how these predators disperse may increase our ability to utilize them as effective biological control agents. Samples were then analyzed with enzyme-linked immunosorbent assay (ELISA) to detect the protein marks. This analysis suggests that some small fraction of the Lygus hesperus population and a portion of the community of predators disperse strikingly long distances. This result implies that long-distance dispersal may be an important factor in the colonization of California cotton fields, and suggests that the movement of agricultural insects should be considered on the landscape scale.