Western corn rootworm (Coleoptera: Chrysomelidae) beetle emergence from weedy Cry3Bbl rootworm-resistant transgenic corn.

Three greenhouse experiments were conducted to evaluate western corn rootworm, Diabrotica virgifera virgifera LeConte, beetle emergence from individual pots containing glyphosate-tolerant transgenic corn, Zea mays L., expressing the Cry3Bbl endotoxin from the soil bacterium Bacillus thuringiensis Berliner (MON863), nontransgenic glyphosate-tolerant isoline corn, grassy weeds (giant foxtail, Setariafaberi R.A.W. Herrm; and large crabgrass, Digitaria sanguinalis (L.) Scop.), and combinations thereof infested with 40 neonate larvae. In the first two experiments, pots with corn and weed combinations were treated with glyphosate 5 d after larval infestation to kill the weeds. The third experiment was similar to the first two except that untreated corn-weed combinations were added. In all three experiments beetle emergence varied significantly. Beetle recovery generally did not vary between the nontransgenic, nontransgenic + weeds, and MON863 + weeds. Significantly more beetles were recovered from MON863 + weeds than MON863 alone or weeds alone. Beetle emergence from MON863 + weeds was likely enhanced by larvae that initially survived on weeds before application of glyphosate. Preliminary data indicated that fecundity was highest from beetles reared on nontransgenic isoline corn and fewer eggs were laid by beetles reared on MON863 alone. Egg viability was generally lowest from beetles reared on MON863. The implications of these results in relation to insect resistant management are discussed.