Pesticidi i Fitomedicina (Jan 2011)
Effects of Spinosad and Abamectin on different Populations of Rice Weevil Sitophilus oryzae (L.) in Treated Wheat Grain
Abstract
In laboratory conditions (25±1ºC and 60±5% r.h.) effects of natural insecticides spinosadand abamectin on five S. oryzae populations (laboratory, Šid, Gornji Milanovac, Žabariand Novi Pazar) were investigated. Both insecticides for all tested populations were appliedto untreated wheat grain at following rates 0.25, 0.5, 1.0 and 2.0 mg AI/kg, subsequently25 adults were added in each plastic vessels (V=200 cm3) containing 50 g of treated wheat,in four replicates, for each population tested. Mortality of weevils was determined after 2-,7- and 14-days, and the effect on progeny production was determined 8-weeks from parentalexposure.Efficacy of spinosad and abamectin after 2-days of weevil exposure for all tested populationsand all application rates was <15%. After 7-days of exposure, the efficacy was ≥95%for weevils from Žabari, in wheat treated with 2 mg/kg of spinosad and abamectin, andfor weevils from Gornji Milanovac, only in wheat treated with 2 mg/kg of spinosad. After14-days of exposure the efficacy ≥95% was found for laboratory weevils and weevils fromŽabari and Gornji Milanovac, in wheat treated with 1 and 2 mg/kg of spinosad, and for S.oryzae from Novi Pazar and Šid, in wheat treated with 2 mg/kg of spinosad. At the same timefor all tested populations abamectin at rates of 0.5, 1.0 and 2.0 mg/kg was 94-100% efficient. No insecticide achieved total (100%) progeny reduction in tested populations of S.oryzae, while high progeny reduction (≥95%) was found only in weevils which were in contactwith wheat treated with 1 and 2 mg/kg of abamectin. The results showed that for highlyefficient control of different populations of S. oryzae in wheat grain, ≥2 mg/kg of abamectin,and, particularly, spinosad should be applied.
