Effect of different spring diapause conditions on adult longevity and survivorship of Cephus cinctus (Hymenoptera: Cephidae) and Bracon cephi (Hymenoptera: Braconidae)

Wheat stem sawfly, Cephus cinctus Norton (Hymenoptera: Cephidae), is a long-standing pest of wheat Triticum aevstivum L. (Poaceae) in the northern Great Plains region of North America. Larval feeding damage inside wheat stems causes decreased head kernel weights, reduced photosynthetic capacity, and contributes to yield losses. Serious C. cinctus infestations can cause economic losses exceeding over $400 million CAD annually. Recently, a bioclimatic model for C. cinctus was developed for the Canadian Prairie region, but the model lacks forecasting capabilities because we lack understanding of overwintering and early spring population dynamics, including how prevailing early season weather patterns affect C. cinctus development and survival. The purpose of this study was to measure the effects of different spring diapause conditions and developmental times on the subsequent life history traits of adult C. cinctus and Bracon cephi Gahan (Hymenoptera: Braconidae), a native parasitoid of C. cinctus. Field-collected individuals were reared under two different temperature regimes to generate two distinct emergence groups for adult survivorship and longevity comparisons. The results of this study will improve our current understanding of how early season weather can affect C. cinctus population dynamics, and contribute to the development of a forecast model for C. cinctus.