Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 4/18/2002
Publication Date: N/A
Interpretive Summary: Many kinds of stink bugs (family Pentatomidae) are important agricultural pests, although some stink bugs are beneficial predators of other insect pests. The attractant chemicals (pheromones) that some stink bugs use to find one another have been identified, and it has been discovered that certain parasitic flies (family Tachinidae) home-in on pheromones as a way to find potential hosts to parasitize. Tests were conducted in the laboratory and the field to determine if particular chemicals affect the behavior of parasites and their host stink bugs differently, and to determine if hidden strains of parasites exist in nature based on differing sensitivity to the pheromones of potential host stink bugs. A common defensive compound characteristic of stink bugs (octenal) was shown to inhibit pheromone attraction of the bugs, but sometimes increase the attraction of the parasites. In addition, evidence indicated that cryptic strains of tachinid parasites do exist in nature. This information is particularly important for scientists involved in manipulating these kinds of parasites for biological pest control, since selecting the wrong chemosensory strain of parasite could lead to failure due to an inability of the parasite to recognize the pest.
Technical Abstract: Tachinid flies commonly use the pheromones and allomones of stink bugs (Pentatomidae) as host-finding kairomones. Pheromone-baited traps for predaceous (Podisus spp.) and phytophagous (Euschistus spp.) pentatomids were used to obtain tachinid parasitoids in order to study the semiochemical relationships between these parasitic flies and their stink bug hosts. Gas chromatography-electroantennogram detector (GC-EAD) experiments and field tests were conducted 1) to determine if pheromone strains of the tachinids, Euclytia flava and Hemyda aurata, occur in nature and, 2) to determine if the EAD-active allomone compound, (E)-2-octenal, affects attraction of Podisus spp. and their tachinid parasitoids to synthetic Podisus pheromones. Addition of (E)-2-octenal to Podisus spp. synthetic pheromones in field traps tended to suppress attraction of the bugs, whereas (E)-2-octenal decreased, did not affect, or increased pheromonal attraction of tachinid parasitoids depending on the host specie pheromone being tested and the habitat type in which the traps were deployed. Evidence gleaned from GC-EAD experiments of E. flava associated with different stink bug hosts suggested that kairomone-strains of this tachinid parasitoid do coexist naturally. The significance of cryptic kairomone strains of parasitoids for classical biological control is discussed, and the mechanisms whereby parasitoids evolve kairomonally mediated host-shifts is considered.