A female wheat stem sawfly resting on wheat awns. (5/15/12)
The wheat stem sawfly, Cephus cinctus, is having a boom year in 2012. This insect is a pest of wheat. The female sawflies (pictured above) deposit a single egg into a wheat stem (a single female sawfly will visit at least 10 wheat stems to deposit her eggs). The larvae that result will feed inside the hollow wheat stem until they are large enough to pupate. At that time the larva will move down the stem and make a pupal chamber near the wheat crown. However, before it develops into a pupa, the larvae will cut the wheat stem a few inches above the pupal chamber. This cutting activity (with the assistance of the wind) will cause the wheat tiller to fall, taking the wheat head and its grain with it to the ground. This year I have had numerous producers and crop scouts commenting on their presence. Locations that normally have infestations are reporting high numbers of sawflies and they are being found in locations where they have not been normally seen before. Unfortunately, there is little that can be done. Chemical control is not effective in their control. We currently do not have high-yielding winter wheat varieties with resistance against this insect. As I've briefly mentioned before, I am on the hunt to locate beneficial insects that might reduce their numbers. I currently have more than 30 wheat fields enrolled in a survey to determine the current distribution of the wheat stem sawfly and the parasitoid wasps that attack it. My lab is collecting as many production practices that we can from the producers that manage these fields. With any luck, I hope to find relationships between production practices and what roll they might play in mitigating sawfly numbers or in improving habitat quality for its natural enemies.