Russian wheat aphid and drought stresses in wheat: tritrophic interactions with Diaeretiella rapae and plant resistance

Abstract

The Russian Wheat Aphid (RWA), Diuraphis noxia (Mordvilko) (Homoptera: Aphididae), has become a serious pest of grain production in North America. Unexpanded (rolled) leaves caused by RWA feeding serve as refugia for the aphid colonies and may limit effective search and attack by aphid parasitoids. Initial investigations on tritrophic interactions with resistant wheat (’TAM W-107’), RWA, greenbug, Schizaphis graminum (Rondani) and the aphid parasitoid Lysiphlebus testaceipes (Cresson) were completed (Campbell et al., 1990). More recently, Reed et al. (1991) found that a tolerant RWA resistant wheat (PI 372129) was beneficial for parasitoid action because the extent of leaf rolling was substantially reduced. Virtually nothing is known of the interactions of drought, RWA, plant resistance and biological control agents. This study was undertaken to investigate such interactions using seedlings of susceptible (’TAM W-101’) or resistant (PI 372129) wheat, RWA and the parasitoid Diaeretiella rapae McIntosh.