Abstract
Two different formulations of diflubenzuron (Micromite® 4L and 80WG) and FC 435-66 spray oil were applied to 'Redblush' grapefruit trees to determine the duration of residual activity on Diaprepes abbreviatus (L.) Coleoptera: Curculionidae egg development. Observations were made on the period to eclosion and the extent of egg mortality per week for each treatment. The effect of the chemical residue present on the leaf surface presented to the weevils as oviposition sites over an extended period of 13 weeks was emphasized. Ingestion of diflubenzuron by adult weevils was not a factor in this study. Based on Kruskal-Wallis ANOVA by ranks, percent mean mortality for the eggs deposited on treated leaves with diflubenzuron were significantly higher over time (p 0.05) than the untreated control and spray oil treated leaves. Although the 80WG formulation caused greater egg mortality than the 4L formulation, the trend was not statistically significant. There was also a significant increase in the developmental time from oviposition to ecolsion for eggs deposited on leaves treated with both formulations of diflubenzuron.
