Monday, December 10, 2007 - 8:05 AM

In-field volatile production of wheat plants infested by wheat stem sawfly, Cephus cinctus (Hymenoptera: Cephidae)

Oscar G. Pérez,, David K. Weaver,, Perry R. Miller,, and Wendell L. Morrill, Montana State University, Land Resources and Environmental Sciences, 334 Leon Johnson Hall. PO Box 173120, Bozeman, MT

The wheat stem sawfly, Cephus cinctus, is a pest of wheat in the Northern Great Plains of North America. It spends most of its life cycle inside the wheat stem, and is difficult to control. Volatile compounds produced by wheat plants that are infested by wheat stem sawfly are being studied to characterize potential semiochemicals used in the host seeking behavior of endemic braconid parasitoids. Such compounds are also a potential tool for enhancing parasitoid suppression of this pest. The objective of this study is to determine the identity and amounts of volatiles produced by uninfested wheat plants in comparison to those that have been infested by wheat stem sawfly under field conditions. We also assessed the effectiveness of an open portable system used to collect the airborne compounds. Volatiles were successfully collected from naturally infested and uninfested wheat plants in fields near Churchill, Gallatin County, Montana during the summers of 2004-2006. Volatile collections were conducted using an open portable volatile collecting system during the final month before the wheat was harvested, which is during the flight period of the larval parasitoids. Several compounds known to induce behavioral responses in adult wheat stem sawflies were in greater amounts in the infested plants, but no unique compounds were evident. The portable collection system proved to be an effective method to collect potential semiochemicals under field conditions. These results provide valuable information toward understanding the host seeking behavior of these endemic sawfly parasitoids.

Species 1: Hymenoptera Cephidae Cephus cinctus (wheat stem sawfly)
Species 2: Hymenoptera Braconidae Bracon cephi
Species 3: Hymenoptera Braconidae Bracon lissogaster