With wheat stem sawfly natural enemies in demand, Montana State University entomologists are investigating ways of increasing their availability.

This fall, the entomologists are concluding a two-year study that involved mass-rearing parasitic wasps that attack wheat stem sawfly larvae that tunnel the interior of developing wheat plants. The team includes entomologists David Weaver, master's graduate Godshen Pallipparambil-Robert and undergraduate Melissa Frazier of Kalispell.

Pallipparambil-Robert's work, as part of his completed master's degree, used large cages placed over wheat at the Post Agronomy Farm west of Bozeman, Mont. He deliberately infested the enclosed wheat with wheat stem sawflies, and then introduced the parasitic wasps. His research explored whether supplemental food provided as nectar from flowering plants or as honey water increases the number of parasitic wasps produced in each cage. Another part of his thesis project examined whether using special ultraviolet and visible light-transmitting windows increases the number of parasites.

"After two years, the research shows that the added light consistently causes small increases in the number of parasitic wasps, while the food supply is probably not important in these mass-rearing cages, because the parasitoids were added in large numbers, and attacked the available sawflies before the need to feed may have become critical " Weaver said. At lower parasitoid densities, supplemental food might be much more important, and research from other systems suggests that this is definitely true in natural settings. However, the goal of the research is to find ways to increase the supply of parasitoids from a controlled system to Montana wheat growers.

"Right now, the number of people wanting parasitic wasps far out-number what we can deliver," he said. The small, orange parasitic wasps are part of the naturally occurring suppression of wheat stem sawfly that varies g
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Contact: David Weaver
weaver@montana.edu
406-994-7608
Montana State University
6-Oct-2006