JOINT ACTION OF A JUVENILE HORMONE ANALOGUE WITH BENZOYLPHENYLUREAS INGESTED BY WESTERN SPRUCE BUDWORM, CHORISTONEURA OCCIDENTALIS (LEPIDOPTERA: TORTRICIDAE)

Mixtures of the juvenile hormone analogue (JHA) methoprene and each of three benzoylphenylureas (BPUs) were fed to sixth-instar western spruce budworm, Choristoneura occidentalis Freeman. The BPUs tested were diflubenzuron, BAY SIR 8514 (N-[(trifluoromethoxy)phenyl]carbamoyl-2-chlorobenzamide), and EL-127063 (N-[[[5-(4-bromphenyl)-6-metnyl-2-pyrazinyl]amino]carbonyl]-2-chlorobenzamide). Mixtures consisted of JHA:BPU combined in 1:9 proportions. Ingestion of methoprene combined with BAY SIR 8514 or diflubenzuron resulted in significantly lower mortality than expected under a simple model of uncorrelated, independent action. Ingestion of the mixture of methoprene and EL-127063, however, resulted in significantly enhanced toxicity over the upper response range (> 50% mortality).