Lethal and sublethal effects of Eforia on the reproduction, development and feeding behavior of Ommatissus lybicus (Hemiptera: Tropiduchidae)

Abstract

Dubas bug, Ommatissus lybicus de Bergevin (Hemiptera: Tropiduchidae), is one of the most important pests of date palm (Phoenix dactylifera L.) in Iran. In the present study, the lethal and sublethal effects of commercial formulations of acetamiprid, clothianidin, diflubenzuron, Eforia® (thiamethoxam+lambda-cyhalothrin), and fenitrothion on O. lybicus were examined. The concentrations of tested insecticides were predetermined by concentration-setting experiments based on a logarithmic scale. Stock solutions of the compounds were prepared by diluting the stock solution in Triton X-100 (0.1%) in distilled water. Triton X-100 (0.1%) in distilled water was used as control. Among insecticides tested, Eforia and fenitrothion were the more toxic to O. lybicus adults with the LC50s of 7.2 and 9.4 mg/L. The sublethal effects of Eforia were assessed by treating O. lybicus adults with the LC10 (3.7 mg/L), LC30 (4.8 mg/L), and LC50 (7.2 mg/L). The significant differences were not found for nymphal development and fecundity in LC10 concentration (73.51 d and 86.24 eggs/female, respectively) compared to control (73.78 d and 84.52 eggs/female, respectively). However, a significant reduction in survival and growth rate was observed in this concentration. The longevity and fecundity of females exposed to LC30 and LC50 concentrations were reduced. At LC30 and LC50 concentrations, Eforia prolonged the developmental duration (80.91 and 84.08 d, respectively) and decreased the survival rate (54.3 and 33.7%, respectively) of immature stages of O. lybicus. Furthermore, the quantity of food assimilated by O. lybicus on the date palm was significantly reduced at the LC30 and LC50 concentrations (1.67 and 1.34 mg, respectively). Altogether, these results indicate that Eforia could be useful for the management of O. lybicus population in Iran.