Effects Of Several Insecticides On Lipaphis Erysimi And Arthropod Community In Autumn Cabbage Fields

The effects of several insecticides on Lipaphis erysimi and the arthropod communityin autumn cabbage fields were studied based on the methods of pesticide bioassay inlaboratory and the field experiment. The main results were as follows:1Toxicity of several insecticides to Lipaphis erysimi in laboratoryThe results of the laboratory tests showed that abamectin had very hight toxic effecton L. erysimi and its LC50was only0.3910mg/L. Clorantraniliprole was mainly used tocontrol Lepidoptera pests, but also had some toxic effect on L. erysimi with LC50of731.3075mg/L. Pymetrozine had relatively low toxic effect on L. erysimi with LC50of1571.0862mg/L in laboratory in24h for its slow toxic effect, but it had excellent controleffect on L. erysimi in field experiment. Therefore, it was needed to test further the toxicityof pymetrozine to L. erysimi in48h.The synergism of abamectin+pymetrozine mixture and pymetrozine+clorantraniliprole mixture was remarkable with the co-toxicity coeffieient of447.5and391.9respectively. The abamectin+clorantraniliprole mixture had only additive effectwith the co-toxicity coeffieient of91.2Control effects of several insecticides on Lipaphis erysimi in cabbagefieldsThe results of field experiments showed that the control efficacy of abamectin on L.erysimi was not satisfactory with the control effects of21.96%、30.26%and20.21%respectively1d、3d and7d after application. Clorantraniliprole had nearly the samecontrol effects of abamectin on L. erysimi. Pymetrozine had excellent control efficacy on L.erysimi with the control effects of17.94%、86.93%and97.37%respectively1d、3d and7d after application, though its control effect was relatively slow. Its control effects of3dand7d after application were significantly higher than those of abamectin andclorantraniliprole.The control efficacy of abamectin+clorantraniliprole mixture on L. erysimi was notsatisfactory. The pymetrozine+clorantraniliprole mixture and abamectin+pymetrozinemixture had excellent control efficacy on L. erysimi and their control effects7d afterapplication had no significant difference to that of pymetrozine, In the meantime, they hadwell control effects on Lepidoptera pests. 3Effects of several insecticides on arthropod community in cabbagefields3.1Effects of several insecticides on the major characteristic indices of arthropodcommunity in cabbage fieldsThe research resulds showed that the evenness and the diversity of arthropodcommunity in control plots were very low because turnip aphid occurred seriously this year.Among the several insecticide treatments, the insecticide which had low control efficacyon L. erysimi was not able to raise the diversity of arthropod community effectively. Theinsecticide treatments of pymetrozine, pymetrozine+clorantraniliprole mixture andabamectin+pymetrozine mixture which had excellent control efficacy on L. erysimi wereable to raise the evenness and the diversity of arthropod community greatly and thediversities7d after the insecticide application were10.5、7.5and7.3times those before theinsecticide application and were8.2,4.7and6.3times those of control treatment in thesame time and therefore raised the community stability greatly.3.2Effects of several insecticides on the ratio of natural enemies to insect pests ofarthropod community in cabbage fieldsThe research resulds showed that the abamectin treatment had a slightly negativeimpact on the ratio of natural enemies to insect pests and the clorantraniliprole treatmentand abamectin+clorantraniliprole mixture treatment had a slightly positive impact on it ascompared with control treatment. The treatments of pymetrozine, abamectin+pymetrozinemixture and pymetrozine+clorantraniliprole mixture which had satisfactory controlefficacy on L. erysimi were able to raise the ratio of natural enemies to insect pests greatlyand they were24.1、18.2and14.4times that of control treatment in the same time7d afterthe insecticide application. This indicated that the treatments of pymetrozine, abamectin+pymetrozine mixture and pymetrozine+clorantraniliprole mixture were able to protect andpromote the natural control effects of natural enemies on insect pests in cabbage fields.