A molecular approach for detecting stage-specific predation on Lygus hesperus

Authors: Hagler, James; CASEY, MILES - Former ARS Employee; Hull, Allya; Machtley, Scott

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/12/2020
Publication Date: 12/30/2020
Citation: Hagler, J.R., Casey, M.T., Hull, A.M., Machtley, S.A. 2020. A molecular approach for detecting stage-specific predation on Lygus hesperus. Journal of Insect Science. 20(6). Article 35. https://doi.org/10.1093/jisesa/ieaa136.
DOI: https://doi.org/10.1093/jisesa/ieaa136

Interpretive Summary: The lygus bug is a major pest threat to cotton and many other crops. It reduces crop yields or values via fruit deformation or fruit loss by feeding preferentially on the fruiting structures of plants (i.e., cotton boll, alfalfa seed, strawberry fruit, etc.). Researchers at Maricopa, Arizona developed a novel method for studying predation on the various life stages of lygus. The method consists of tagging lygus eggs, immatures, and adults with unique protein marks. In turn, the uniquely marked lygus life stages consumed by predators can be detected in their guts by a suite of protein-specific assays. Lygus eggs were marked with rabbit serum, while third instar and adults were marked with chicken and rat sera, respectively. Then, the variously labeled lygus bugs were introduced into field cages that enclosed the native arthropod population inhabiting an individual cotton plant. After an exposure period, the predators in each cage were counted and their gut contents were analyzed for the presence of protein-marked prey remnants. The whole-plant sampling scheme revealed that big-eyed bugs and spiders were the numerically dominant predator taxa in the cotton field. The gut content examinations showed that these two taxa appeared to be the most prolific predators of immature lygus. Other key findings include that collops beetles and fire ants appear to be adept at finding and feeding on the cryptic eggs, and that adult lygus, albeit at low frequencies, engaged in cannibalism on immatures. The methods described in this study will be adapted to study other aspects of arthropod predation in the cotton agroecosystem.

Technical Abstract: A molecular gut analysis technique is described to identify predators of Lygus hesperus (Knight), a significant pest of many crops. The technique is unique because it can pinpoint which life stage of the pest was consumed. Sentinel egg masses designed to mimic the endophytic egg-laying behavior of L. Hesperus were marked with rabbit serum, while third instar and adult L. hesperus were marked with chicken and rat sera, respectively. Then, the variously labeled L. hesperus life stages were introduced into field cages that enclosed the native arthropod population inhabiting an individual plant. After a six-hour exposure period, the predator assemblage, including the introduced and native L. hesperus population, in each cage were counted and had their gut contents examined for the presence of the variously marked L. hesperus life stages by a suite of serum-specific enzyme-linked immunosorbent assays (ELISA). The whole-plant sampling scheme revealed that Geocoris spp. and members of the spider complex were the numerically dominant predator taxa in the cotton field. The gut content analyses also showed that these two taxa appeared to be the most prolific predators of the L. hesperus nymph stage. Other key findings include that Collops vittatus (Say) and Solenopsis xyloni McCook appear to be adept at finding and feeding on the cryptic L. hesperus egg stage, and that L. hesperus, albeit at low frequencies, engaged in cannibalism. The methods described here could be adapted for studying life stage-specific feeding preferences for a wide variety of arthropod taxa.