EFFECTS OF ALTERNATIVE HOST PLANTS ON LONGEVITY, OVIPOSITION, AND EMERGENCE OF WESTERN AND NORTHERN CORN ROOTWORMS (COLEOPTERA, CHRYSOMELIDAE)

The longevity of adult female western corn rootworms, Diabrotica virgifera virgifera LeConte, maintained on diets of squash blossoms, sunflower ray florets or inflorescences, and goldenrod inflorescences was significantly reduced compared with beetles maintained on corn ears. However, beetles survived for extended periods on these diets and produced viable eggs. Oviposition rates were inversely proportional to adult longevity so that total oviposition was largely unaffected by diet. By contrast, adult female northern corn rootworms, Diabrotica barberi Smith & Lawrence, showed only minor differences in longevity on the alternative diets. Adult emergence of both species from corn plots previously interplanted with corn, squash, or sunflower in close proximity was similarly distributed among the three parental foods, demonstrating that considerable oviposition occurs where larvae that specialize in corn cannot feed. When emergence was monitored at least 4.5 m away from adjacent host species, significantly more adults emerged from areas previously planted in corn. These results indicate that oviposition near larval food might be directed more by long-range volatiles from corn than by visual or physical attributes of plants within sites. Choice of ovipositional sites and adult foods represents clearly distinct behaviors in female rootworms, and western corn rootworm, in particular, will lay eggs in sites where feeding reduces fitness. © 1990 Entomological Society of America.