The Field Control Of5%Lambda-cyhalothrin/Emamectin Benzoate Ew On Spodoptera Exigua

The beet armyworm, Spodoptera exigua (Hübner)(Lepidoptera: Noctuidae), is apolyphagous insect pest that lives on a wide range of crops, such as including corn, cotton,beet, tomato, celery, lettuce, cabbage, alfalfa and others. In recent years, the outbreaks of beetarmyworm caused vast economic losses. Insecticides have been heavily applied to control thispest; however, the development of insecticide resistance has resulted in control failures andfield resistance cases to conventional insecticides (organophosphates, carbamates andpyrethroids). To date, using chemical insecticides is still the most cost-effective way forcontrolling beet armyworm. In order to delay the development of insecticide resistance andimprove the control efficiency, combined use of different types of insecticides has beenwidely employed in the field control of agriculture pests.In this work, we selected two cabbage fields where the beet armyworm occurs annuallyin Xianyang and Baoji, Shannxi province, and tested the field control efficiency of a newmixed-insecticide,5%lambda-cyhalothrin/emamectin benzoate EW, to beet armyworm. Wereached the following main results:High control efficiencies of5%lambda-cyhalothrin/emamectin benzoate EW at theeffective doses of6g/hectare,7.5g/hectare and9g/hectare to beet armyworm were observedin both testing fields. In Xianyang field, in the second day post applying insecticide, thecontrol efficiencies of effective doses of6g/hectare,7.5g/hectare and9g/hectare were74.78%,84.70%and86.00%, respectively, which increased to81.85%,87.47%and92.03%in the fifth day, and further elevated to85.10%,92.55%,96.46%in the tenth daypost-treatment. As for the control treatments, the control efficiencies of25g/Llambda-cyhalothrin EC with the effective doses of22.5g/hectare and2%emamectin benzoateEC with the effective doses of2.25g/hectare were77.47%,78.67%,72.75%and81.14%,85.15%,92.66%at the second, fifth and tenth day post-treatment, respectively. In Baoji field,in the second day post applying insecticide, the control efficiencies of effective doses of6g/hectare,7.5g/hectare and9g/hectare were91.88%,93.43%and94.97%, respectively, which slightly decreased to90.24%,92.40%and94.63%in the fifth day, and further declinedto89.28%,91.77%and93.80%in the tenth day post-treatment. In the control treatments, thecontrol efficiencies of2.5%lambda-cyhalothrin ME with the effective doses of11.25g/hectare and1%emamectin benzoate ME with the effective doses of1.8g/hectare were91.62%,90.76%,88.97%and91.29%,91.30%,89.30%at the second, fifth and tenth daypost-treatment, respectively.We also found that5%lambda-cyhalothrin/emamectin benzoate EW at differenteffective doses didn’t show negative effect on cabbage growth, as well as on non-targetbeneficial insects. Moreover, toxic activities on other pests, such as the diamondback moth,cabbage worm, and vegetable aphids etc., were also observed.Our results indicated that5%lambda-cyhalothrin/emamectin benzoate EW could controlbeet armyworm effectively, with fast-acting property and long-time effectiveness. Therecommended effective doses are6.0-9.0g/hectare. The application time is at the initial stageof young instar larvae.