Examining the dispersal capabilities of Lygus hesperus and its natural enemy Geocoris pallens in California's San Joaquin Valley
1Department of Entomology, University of California, Davis, CA, USA
2USDA-ARS, Arid-Land Agricultural Research Center, Maricopa, AZ, USA
Correspondence: fjsheller@ucdavis.edu
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 preliminary study we measured the dispersal of L. hesperus and its natural enemies from a cut alfalfa field into adjacent cotton fields. L. hesperus will leave a host field when it becomes unsuitable, usually when it is harvested or senesces. The monthly cutting of alfalfa for hay commonly creates such a scenario. In this experiment we marked a 72-acre alfalfa field that had a substantial density of L. hesperus (6–7 Lygus per 100 sweeps) with a distinctive protein mark (a diluted cow's milk solution). The following day the alfalfa field was cut, presumably forcing its occupants to disperse. Cotton fields adjacent to the eastern border of the cut alfalfa field were sampled the day immediately after cutting and again 6 days later. In addition to Lygus spp., predators including Geocoris spp., Orius insidiosus, Nabis spp., Hippodamia convergens, and Coccinella septempunctata were collected, with the majority of samples collected being Geocoris pallens. 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 mark (3093 individuals). This analysis detected marked L. hesperus up to 800 meters into the cotton field. This preliminary result suggests that some small fraction of a L. hesperus population disperses strikingly long distances and that long-distance dispersal may be an important factor in the colonization of California cotton fields.
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