One aspect of parasitoid host selection is to find the habitat of a potential prey individual. A Y-tube olfactometer was used to evaluate habitat preference of wasps exposed to airborne odors of different grass species. When given a choice between a grass species and air, all three wasp species preferred the grasses most closely related to their original host plants. When given a choice between two grass species, parasitoids sometimes exhibited a preference. Thus far, it seems likely that these parasitoids would have different habitat ranges if released as novel biological control agents.

The divergent habitat preferences shown by these closely related species reemphasizes the need for pre-release testing of novel biological control agents. Future studies will look at additional grass species and at selected non-grass species, and the effect of plant damage on parasitoid habitat preference.

Source:

C. E. Rutledge, Dept. of Entomology, University of Illinois, Urbana IL 61801 and R. N. Wiedenmann, Center for Economic Entomology, Illinois Natural History Survey, Champaign IL 61820. Based on a paper presented at the 1996 North Central Branch meeting of the Entomological Society of America, Omaha, NE.