Parasitism of wheat stem sawfly larvae in barley by two native braconids

Wheat stem sawfly, Cephus cinctus Norton is a serious pest of barley and wheat in western North America. The damaging larval stage is protected inside the host stem. Integrated management centered on host plant resistance and biological control are the best options to reduce economic losses caused by this species in both barley and wheat. The biological control is largely due to Bracon cephi (Gahan) and B. lissogaster Muesebeck. However, barley has greater innate host plant resistance than barley.  A key question is – do barley cultivars that have higher rates of early larval mortality still support parasitoid populations? To do this we examined rates of parasitism in several barley cultivars with varying levels of early larval mortality. Our findings suggest that adult parasitoids are still able to locate relatively rare large C. cinctus larvae in more resistant cultivars. Our findings can be used to further develop management approaches for damaging populations of C. cinctus in barley.