Potential of 8-methyl-2-decyl propanoate and plant-derived volatiles for attracting corn rootworm beetles (Coleoptera: Chrysomelidae) to toxic bait

Populations of Diabrotica virgifera virgifera LeConte (WCR) and D. barberi Smith and Lawrence (NCR) were monitored in plots (15 by 15 m) that contained 5 x 5 grids of toxic baits in vial traps. For plots in which baits consisted of only olive oil plus carbaryl, 0.4 WCR and 3.6 NCR per bait were captured. In plots in which a feeding stimulant (cucurbitacin) was added, capture per bait was 12.4 WCR and 22.3 NCR. Addition of plant-derived volatile attractants (estragole for WCR and eugenol for NCR) increased capture of the respective species another four times. The racemate of 8R-methyl-2R-decyl propanoate (the apparent sex pheromone of both species) caused an increase in numbers of male WCR captured on unbaited sticky traps within plots, but the amount used (900 microgram per bait) was apparently too great for optimal attraction of males to point sources. The racemate also repelled NCR of both sexes. Over 6 d, traps that were baited with estragole and eugenol removed more WCR and NCR than were estimated to have been in the plots at the start of the test; because of immigration, however, there were no detectable reductions in numbers of beetles on plants within those plots. Feeding stimulants and plant volatiles show great promise for enhancing the effectiveness of adulticides, but, because of the beetles' vagility, the concept must be tested over much broader acreages.