GERMINATING CORN EXTRACTS AND 6-METHOXY-2-BENZOXAZOLINONE - WESTERN CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE) LARVAL ATTRACTANTS EVALUATED WITH SOIL INSECTICIDES

6-Methoxy-2-benzoxazolinone (MBOA), a host-location semiochemical for western corn rootworm, Diabrotica virgifera virgifera LeConte, larvae, was tested as an attractant with the experimental insecticide chloret hoxyphos in laboratory and field experiments. Crude dichloromethane ex tracts of germinating corn seedlings were tested as an additional attr actant for incorporation in soil insecticides (chlorethoxyphos and car bofuran) in laboratory experiments. Significantly more western corn ro otworm lan ae were recovered in the core portion of the bioassay appar atus (the portion where the attractant was located) in laboratory expe riments when MBOA or a crude dichloromethane extract of germinating co in seedlings was present with insecticide than in the other three trea tments (attractant alone, insecticide alone, and control), indicating that MBOA or a crude dichloromethane extract of germinating corn seedl ings are behaviorally active to western corn rootworm larvae at ambien t carbon dioxide levels. In these same experiments, significantly more larvae died in the core portion of the bioassay when insecticide was present with an attractant than when insecticide alone or attractant a lone were present, or in the control, indicating that either MBOA or e lude dichloromethane extract of germinating corn seedlings can be used to increase insecticide efficacy in laboratory bioassays. Naturally i nfested and artificially infested field experiments were conducted in 1991 and 1992. Most of the MBOA/chlorethoxyphos combinations did not s ignificantly lower corn rootworm damage when compared to the same leve l of chlorethoxyphos without MBOA. The only MBOA/chlorethoxyphos combi nation that provided significantly reduced corn rootworm damage was th e 1992 naturally infested field experiments in Akron, CO. Treatments w ith granules containing both 2.5% chlorethoxyphos and 3 mg/g MBOA had significantly less corn rootworm damage (lower root ratings) than trea tments with 2.5% chlorethoxyphos without MBOA. Western corn rootworm l arvae are very sensitive to MBOA levels. The single attractant MBOA, t hough promising in laboratory studies, did not consistently increase t he efficacy of chlorethoxyphos under the variable conditions of field studies.