Parasitoids of the Consperse Stink Bug (Hemiptera: Pentatomidae) in North Central Washington and Attractiveness of a Host-Produced Pheromone Component

The parasitoid complex of the consperse stink bug, Euschistus conspersus Uhler, was investigated in a series of field experiments conducted in native vegetation surrounding commercial apple orchards in the state of Washington. Rearing of parasitoids from adult E. conspersus confirmed the presence of two tachinid species, Gymnosoma filiola Loew and Gymnoclytia occidentalis Townsend. Three species of scelionids were reared from fresh egg masses placed on mullein plants (Verbascum thapsus L.) with Trissolcus utahensis (Ashmead) being the most common species. Though some parasitism was recorded in all study sites by both tachinids and scelionids, overall levels of parasitism were low (<10%). Predation comprised the major source of egg mortality in the field. Bucket traps baited with the male-produced aggregation pheromone component, methyl (2E,4Z)-decadienoate, captured significantly more G. occidentalis than unbaited controls, suggesting that it may use this compound as a host-finding kairomone. A test comparing E. conspersus egg masses placed on baited vs. unbaited V. thapsus revealed no differences in the rate of parasitism by scelionid parasitoids.