Community Characteristics And Toxic Effect Of Insecticides On Natural Enemies Of Insect Pests In Summer Corn Fields

This article studies on the structure character of pests and natural enemies community and affection of pesticide to natural enemies in summer corn fields,which could help us proceed biocontrol preferably. The conclusions are as follows:1 The natural enemies items was made,there are 34 species in all arthropod,partly of 5 orders and 15 families.The preponderant species are ladybug,lacewings and bugs,these natural enemies play an important role in pests management.The Coleoptera pests is the most,accounts for 55.6517%,the spiders accounts for 30.5652,the Chryspidae accounts for 6.7474%,the Hemiptera accounts for2.9412%, and the others accounts for 4.0946%.The dominant species are Propylaea japonica(Thunberg) and Harmonia axyridis(Pallas),these two accounts for 53.4025%.Besiding,the Erigonidium graminicohm(Sundevall)＞Misumenops tricupidatus(Fabricius).＞Chrysopa septempunctata Wesmael.＞Theridiou kompirense Boes et Str.＞Chrysopa Formosa Brauer.＞Coccinella septempunctata Linnaeus=Macrocentrus cingulum Brischke.＞Chrysoperla sinica(Tjeder).Because there are so much rain the lacewings and the Syrphidae are evidently less.Based on above,the target of toxic effect should be chosen Harmonia axyridis(Pallas), Propylaea japonica(Thunberg),Coccinella septempuctata L.,which have important practical meaning and scientific value.2 The ladybug can be protected when spraying pestisides scientifically and timely.The result shows that every state of the ladybug has different sensitivity when spraying pestisides,and the larva show us sensitive.So when we spraying pestisides,we shoud avoid the fastigium of the larva.At the same time we should actualize comprehensive treatment,and the dosage should,be paid attention to.