Study On Green Control Tactics Against White Grubs In Peanut Fields In Shandong Province

Peanut is a kind of important economic crops in Shandong Province, which plays an irreplaceable role in the national economy. However, peanuts yield reduces severely when affected by underground pests. White grub, the general term of Coleoptera Scarabaeoidea larva, is the main underground pest. Different dominant grub species occur in different places and have different biological characteristics, thus investigation into the dominant grub species in different places is the premise of taking control over them. The control on underground pests mainly relies on chemicals. The excessive use of chemicals can not control underground pests effectively, however, pesticide residues in peanuts may threat human health and affect peanut export. Under field survey on peanuts producing areas in Shandong Province, this article describes the differences in grub distribution. An underground pest prevention scheme of low toxicity, high efficiency is raised to achieve green control of white grubs. The main results are as follows:1. Great distribution differences exist in the main peanuts producing areas in Shandong Province.The dominant grub species in Yantai is Holotrichia parallela Motschulsky. The proportion of this species can reach83.33%～100.00%in some places. Maladera ovatyla occurs seriously in Zoucheng, accounts for66.67%～100%. Tanyproctus parvus occurs in the west of Fuqiujia village in Xiangcheng Town, whose proportion in underground pest is20%. Anomala corpulenta Motschulsky’s proportion in another field in the same village is33.33%. The dominant underground pest in peanut field is Holotrichia parallela Motschulsky and Hloltrichia diomphalia Batesa The proportion of Holotrichia parallela Motschulsky can even reach90.74%～100.00%. In some fields in Dongshilaier village, Zhangjiayu village and Muchangyu village, Holotrichia parallela Motschulsky is the dominant species and is in the proportion of46.67%、66.13%and67.86%, respectively.2. In field experiments by root-irrigation we found that better results occurred in all test areas than the control areas. The number of white grubs in groups tested with nematodes X-7is even less than the groups controlled by chemicals, what’s more, the yield is higher. Thus nematodes X-7is the ideal pesticide to control white grubs in peanuts fields. Though the effect of biological agent on controlling pests and increasing yield is not as good as chemicals, no significant differences show. We can come into a conclusion that biological agent can take the place of chemicals to some extent.3. By comparing the various indicators of different planting mode,we find that average pods of mulched spring peanuts with soil covered is highest,16.90, the average pods of mulched spring planting peanuts is16.26, the average pods of opened spring peanut was13.91.After plastic-film covering with soil covered or plastic-film covering only, the rate of damaged plant, rate of damaged pod and grubs were lower than the opened field mode.The highest average pods of summer peanuts after soil covered is10.24,average pods of mulched summer peanuts is9.78, the average pods of opened summer peanuts is9.45. After plastic-film covering with soil covered or plastic-film covering only, the rate of damaged plant, rate of damaged pod and grubs were lower than the opened field mode.