Review of wheat stem sawfly (Cephus cinctus)

The wheat stem sawfly (WSS), Cephus cinctus Norton, is a hymenopteran of the family Cephidae and broadly distributed across the United States and Canada. In the northern Great Plains, from Colorado into Canada, it is a pest of wheat, Triticum aestivum L. The stem-feeding larvae of this insect cause yield reduction through damage of the plant’s vascular system and by stem girdling causing plant lodging. In Nebraska, the pest status of the WSS has fluctuated. However, with increased adaptation to winter wheat through the 1990s, the pest status of WSS has increased. The increase of minimum or no-till practices to reduce erosion and conserve moisture, especially in response to recent drought conditions, has likely increased sawfly survival. The lifecycle of the WSS and wheat production practices pose challenges for effective management. In Nebraska, the sawfly emerges from late May to early June. Females mate and seek out nearby hosts for oviposition. After hatching, the larva tunnel down the stem, and only one larva will survive per stem due to larval cannibalism. In early July, they girdle the inside of the stem, plug it with frass, and undergo diapause near the crown. After diapause, they complete development in the stem before emerging as adults over a 4-5 week period. Due to the extended emergence period and protection offered by the stem, chemical control is not effective. Current management recommendations are the use of solid-stem wheat cultivars to reduce lodging or rotation to a non-host crop.