Development and application of a glassy-winged and smoke-tree sharpshooter egg-specific predator gut content ELISA

The recent invasion of southern California by the glassy-winged sharpshooter (GWSS), Homalodisca coagulata (Say) (Hemiptera: Cicadellidae), has triggered a statewide control effort. Management of GWSS will include biological control using resident and imported natural enemies. Currently, very little information is available on the role of generalist predators in suppression of GWSS eggs, nymphs or adults. We have developed a sharpshooter egg-specific monoclonal antibody (MAb) for use as a diagnostic tool for predator gut content analysis. The MAb was tested by an indirect enzyme-linked immunosorbent assay (ELISA) for specificity to the different life stages of GWSS, smoke-tree sharpshooter (STSS), Homalodisca liturata Ball (Hemiptera: Cicadellidae), and various life stages of 27 other arthropod species. We found that the MAb only reacted to the egg stage of both sharpshooters and, to a lesser extent, to the adult stage of gravid GWSS and STSS females. Moreover, the ELISA was more responsive to younger GWSS eggs than older ones. Laboratory trials were conducted to determine how long GWSS egg antigen remained detectable in the guts of the green lacewing, Chrysoperla carnea Stephens (Neuroptera: Chrysopidae) and the ladybird beetle, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae) using both an indirect and sandwich ELISA format. We found that GWSS egg antigen was detectable for up to 30 and 12 h in the guts of C. carnea and H. axyridis; respectively, and that the sandwich ELISA was much more sensitive than the indirect ELISA. Finally, 98 field-collected lacewings were examined for sharpshooter remains using our sharpshooter-specific sandwich ELISA. The assay detected sharpshooter egg antigen in 8.2% of the lacewings examined. This work represents a first step towards identifying the GWSS predator complex.