Impact of Lavandula officinalis, inert dusts and their formulations on Sitophilus oryzae

Abstract

The volatile oil (Lavandula officinalis L.) and the inorganic compounds (inert dusts), aluminum oxide, kaolin and silicon dioxide were screened individually and in formulations against the rice weevil, Sitophilus oryzae. Aluminum oxide was the most potent with LC₅₀ value of 0.65 mg/cm², followed by silicon dioxide with LC₅₀ value of 0.96 mg/cm², while, kaolin gave LC₅₀ value of 9.29 mg/cm². The cumulative mortality (0-50, 50-100, 100-150, 150-200, 200-250, 250-300 days) responses at exposure times of L. officinalis and the inert dusts as well as the inert dust formulations at LC₅₀ concentrations against S. oryzae were investigated. Moreover, the number of the offspring after 50 days of each lifetime period was developed. L. officinalis had a short duration of toxicity, as the efficiency continued only for 2 days from exposure to the compound. Silicon dioxide alone or in formulation was the most powerful, it gave full control of S. oryzae adults after 7 days at four (0-50, 50-100, 100-150, 150-200 days) and five (0-50, 50-100, 100-150, 150-200, 200-250 days) lifetime periods, respectively, in the same trend, silicon dioxide alone or in formulation possessed 100% reduction of the offspring at five life time periods. Moreover, aluminum oxide alone or in formulation gave full control of the insect after 7 days of exposure until three lifetime periods of the compound. Likewise, the compound alone or in formulation, possessed 100% reduction of the offspring at four lifetime periods. The formulations of aluminum oxide and silicon dioxide were more efficient than the compounds treated alone, where the effectiveness increased nearly two times, after 2 days from exposure at first 50 days lifetime period. Likewise, kaolin formulation was more effective than kaolin alone in the same lifetime period.