Host plant interactions between wheat germplasm source and wheat stem sawfly Cephus cinctus Norton (Hymenoptera: Cephidae). II. other germplasm

The wheat stem sawfly (WSS) Cephus cinctus Norton (Hymenoptera: Cephidae) is an economically destructive insect pest of wheat in the northern Great Plains. Solid stem cultivar selection is one critical component to the integrated management of WSS. A significant resurgence of WSS in the southern prairies of Canada caused substantial economic losses from 1999 through 2007, which was compounded by the low adoption rate of solid-stem cultivars. A study was conducted from 2003 to 2005 in southern Alberta and Saskatchewan, Canada: (1) to characterize resistance levels in solid-stem germplasm derived from S615 and alternate genetic backgrounds, and (2) to determine the impact of host plant tolerance on WSS population dynamics. The tetraploid cultivar Golden Ball and its hexaploid derivative G9608B1-L-12J11BF02 were the most consistent at reducing damage, larval growth (fitness), and fecundity of WSS. The challenge will be to maintain this level of efficacy as the Canada Western Red Spring phenotype is reintroduced into the germplasm. Our study suggests solid-stem cultivars are highly effective but prone to inconsistent performance and should therefore be integrated into a holistic strategy for WSS that includes agronomics and biocontrol.