FACTORS AFFECTING CAPTURE OF CORN-ROOTWORM BEETLES (COLEOPTERA, CHRYSOMELIDAE) AT TRAPS BAITED WITH NONPHEROMONAL ATTRACTANTS

Adult western corn rootworm, Diabrotica virgifera virgifera LeConte, and northern corn rootworm, D. Barberi Smith and Lawrence, were captured at white and yellow sticky traps and at traps made from plastic vials that contained a mixture of a toxicant and a feeding stimulant. Over 18 d, capture of western corn rootworm was up to 100 times greater at traps baited with estragole or p -methoxycinnamonitrile (p -MCN) than at unbaited traps; baits of eugenol produced 3- to 50-fold increases in capture of northern corn rootworm. Addition of indole to baits containing estragole or p -MCN had little effect on capture at sticky traps but reduced numbers of both species caught in vials. Daily temperature-activity indices, based on bi-hourly temperatures and on actograph data from a previously published study, explained 26% (female) and 50% (male) of day-to-day variation in capture for western corn rootworm but only about 8% for northern corn rootworm. Lesser proportions of daily variation in capture were explained by raw temperature data and by measurements of wind, humidity, and numbers of beetles on plants. When traps were baited with 5, 50, or 500 mg of the attractants, catch of northern corn rootworm on sticky traps increased with the amount of eugenol, but catch of western corn rootworm in vials declined with increases in amount of attractant. Dose of attractant had relatively little effect on capture of western corn rootworm on sticky traps or northern corn rootworm in vials. Both species were captured primarily around midday, except that large numbers of northern corn rootworm (particularly males) were also captured on warm nights. © 1990 Entomological Society of America.