Initial Larval Feeding on an Alternate Host Enhances Western Corn Rootworm (Coleoptera: Chrysomelidae) Beetle Emergence onCry3Bb1-Expressing Maize

Abstract

The potential for rootworm larvae to move between grassy weeds and transgenic maize may be important in resistance management of transgenic rootworm-resistant maize. An experiment was conducted under growth chamber and greenhouse conditions to determine the impact of initial feeding of rootworm larvae on alternate hosts, followed by switching host to transgenic maize, on the development of western corn rootworm (Diabrotica virgifera virgifera LeConte). Two grassy weed species, rootworm-resistant Cry3Bb1 transgenic maize (MON863, YieldGardH Rootworm) and its isoline, were infested with 50 neonate larvae per container four weeks after planting. Large crabgrass (Digitaria sanguinalis (L.) Scop), and giant foxtail, Setaria faberi R. A. W. Herrm both in the Poaceae, were chosen because they were relatively good hosts in previous studies. On the 5 th ,1 0 th , and 15 th d after infestation, the Tullgren funnel technique was used to facilitate larval movement (host-switching) from the original host plants to the final hosts (MON863 or its isoline). Beetle emergence and fecundity were significantly impacted by the original host, the final host, and their interaction. The original and the final host plant also significantly impacted the sex ratio of the beetles. The host-switching date did not impact any of those three variables. Only the original host had a significant impact on egg viability. Significantly more reproductively fit beetles were produced from larvae that fed on an alternate host before moving to transgenic maize than from larvae fed exclusively on transgenic maize. Interactions with alternate hosts may influence transgenic maize resistance