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 chlorethoxyphos in laboratory and field experiments. Crude dichloromethane extracts of germinating corn seedlings were tested as an additional attractant for incorporation in soil insecticides (chlorethoxyphos and carbofuran) in laboratory experiments. Significantly more western corn rootworm larvae were recovered in the core portion of the bioassay apparatus (the portion where the attractant was located) in laboratory experiments when MBOA or a crude dichloromethane extract of germinating corn seedlings was present with insecticide than in the other three treatments (attractant alone, insecticide alone, and control), indicating that MBOA or a crude dichloromethane extract of germinating corn seedlings are behaviorally active to western corn rootworm larvae at ambient 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 alone were present, or in the control, indicating that either MBOA or crude dichloromethane extract of germinating corn seedlings can be used to increase insecticide efficacy in laboratory bioassays. Naturally infested and artificially infested field experiments were conducted in 1991 and 1992. Most of the MBOA/chlorethoxyphos combinations did not significantly lower corn rootworm damage when compared to the same level of chlorethoxyphos without MBOA. The only MBOA/chlorethoxyphos combination that provided significantly reduced corn rootworm damage was the 1992 naturally infested field experiments in Akron, CO. Treatments with granules containing both 2.5% chlorethoxyphos and 3 mg/g MBOA had significantly less corn rootworm damage (lower root ratings) than treatments with 2.5% chlorethoxyphos without MBOA. Western corn rootworm larvae are very sensitive to MBOA levels. The single attractant MBOA, though promising in laboratory studies, did not consistently increase the efficacy of chlorethoxyphos under the variable conditions of field studies.