Study On The Efficacy Of Spinosad Against Stored-product Insects In Wheat

Toxicity of spinosad on adults of Sitophilus oryzae (Linnaeus), Sitophilus zeamais( Motschulsky ) , Rhyzopertha dominica (Fabricius), Tribolium castaneum (Herbst), Oryzaephilus surinamensis (Linne), Cryptolestes ferrugineus (Stephens), Liposcelis entomophila (Enderlein) and Liposcelis bostrychophila (Badonnel) was investigated by the FAO standard method——filter paper method,and compared with the Avermectin,Osthole and Pirimiphos-methyl. Phosphine resistance strains of S. oryzae, R. dominica and T. castaneum were tested with the same method to research the cross resistance of spinosad and phosphine respectively. In the method of laboratory efficacy test simulation the condition of the storage, spinosad and pests were mixed up into the grain per kg, comprehensive evaluation of the efficacy of Spinosad and set different moisture of wheat to explore the relationship between the moisture and the efficacy of Spinosad. The results were followed:The LD50 in 24h of S. oryzae, S. zeamais, R. dominica, O. surinamensis, C. ferrugineus and L. entomophila were 0.344 mg/cm2,0.125 mg/cm2,0.0096mg/cm2,0.0246mg/cm2,0.0121mg/cm2,0.1741mg/cm2 for spinosad respectively. The LD50 in 48h of T. castaneum and L. bostrychophila were 3.1673 mg/cm2,6.9925 mg/cm2 for spinosad respectively. The toxicity of spinosad was R. dominica > C. ferrugineus > O. surinamensis > S. zeamais > L. entomophila>S. oryzae>T. castaneum>L. bostrychophila.The toxicity of spinosad,Avermectin,Osthole and Pirimiphos-methyl to S. zeamais,R. dominica,O. surinamensis were Osthole>Pirimiphos-methyl>spinosad>Avermectin, to C. ferrugineus were Pirimiphos-methyl>Osthole>spinosad>Avermectin.The results indicated that there was no obvious toxicity difference of spinosad to phosphine resistant strains of S. oryzae, R. dominica and T. castaneum. Spinosad can prohibit the emergence of offspring of S. oryzae, R. dominica and T. castaneum both for phosphine resistance and susceptible strains. There was no cross resistance of spinosad to phosphine resistance S. oryzae, R. dominica and T. castaneum.In the experimental doses, poor preventive effect of spinosad to offspring of S. oryzae and S. zeamais ;the effect on the R. dominica and C. ferrugineus is better ,and the effect can last for 6 months and 4 months respectively ; but the effect to the T. castaneum is not so ideal. spinosad to control its population, higher the dose is , number of its population is smaller. The efficacy of spinosad efficacy was effected by the moisture of the wheat. S. zeamais was not so sensitive to spinosad, moisture of wheat does not affect the efficacy of spinosad on adult, however, a greater impact on the offspring results, high moisture corn, wheat, as the number of offspring was significantly higher than the low water content of wheat. However, spinosad on the more sensitive R. dominica and the C. ferrugineus, there was no significant difference in the efficacy of spinosad in the wheat with the different moisture content . The efficacy of spinosad will not impact by the moisture of the wheat.Spinosad in real storage test dose,had a good effect on the powder feeding insect such as C. ferrugineus and T. castaneum, as well as the Linposcelis paeta (Pearman), but the efficacy on the boring pest of S. zeamais was not satisfactory . The vast majority of insect pests was S. zeamais , control the populations of S. zeamais was the focus of the work in storage experiments,especially to the hidden insect. Compared with spinosad, the efficacy of methyl parathion pyrimidine to storage pest is more significant.In the one year's time of wheat storage , the pest prevention and control should be taken in one month after harvest, that is from July to August, will reduce the losses of stored grains substantially, according to the temperature effect on the insect growth and development.