Effect of Alsystin and Diflubenzuron on the Rice Water Weevil (Coleoptera: Curculionidae)

Abstract

Two benzoylphenyl ureas (BPU), alsystin and diflubenzuron, were each tested at a dosage of 0.28 kg (AI)/ha in the greenhouse and laboratory on wild-caught adults of Lissorhoptrus oryzophilus Kuschel to determine the effects of the chemicals on oviposition and immature progeny. Studies showed significant reductions in the number of immatures that developed when either BPU was applied either to rice foliage or to water (containing submerged rice stems with eggs) immediately after oviposition. Applications of either BPU to water at intervals of 5, 9, and 14 days after oviposition showed no significant reductions in numbers of immatures. There were no significant differences in numbers of eggs deposited following contact of adults with treated foliage, regardless of whether immediate or residual effects (up to 6 days) were examined. Either BPU applied to rice foliage to contact adults or to water immediately after oviposition resulted in significantly fewer first instars. First instars treated directly in a suspension of either BPU showed no mortality.