Assessment of the efficacy of spinetoram and spinosad against adults of three Sitophilus species reared on four different winter wheat varieties

Abstract: The efficacy of spinetoram and spinosad against 2-4 weeks old Sitophilus adults has been tested under laboratory conditions. Spinetoram and spinosad were applied at three different dose rates (0.5., 1 and 2 mg/kg). Experiment was performed at 25 °C and 65% rh, on four different winter wheat varieties. Mortality counts were assessed on day 7, day 24 and day 21. Our research demonstrated impact of grain type, dose of exposure, day of evaluation and Sitophilus species on mortality of weevils. Mortality of weevils was higher in treatments treated with spinetoram (90.19 ± 0.48%). After day 21, spinosad caused 91.64 ± 0.93% mortality, meanwhile 96.13 ±0.51% mortality was detected in spinetoram treatment after day 21. When applied spinosad as 2 mg/kg, 96.35 ± 0.44% was detected. Spinetoram caused 96.79 ± 0.38% at 2 mg/kg. Efficacy of spinosad (69.47 ± 1.87%) and spinetoram (78.23 ± 0.83%) was the lowest on variety ‘Fidelius’. Spinosad caused the highest mortality in treatments with Serbian maize weevil (96.64 ± 0.31%), meawhile spinetoram prooved to be the most efficient in treatments with Serbian rice weevil (94.58 ± 0.77%) and Serbian granary weevil (94.07 ± 0.64%). Our resarch on the efficacy of spinetoram and spinosad against stored product insect pests is the first one for Slovenian agriculture. It presents good basics for further studies on implementation of tested insecticides as protectant of stored grains in Slovenia.