The Study Of Biological And Chemical Control On Thrips Flavidulus

Four thousand years ago, Chinese ancestors began to plant citrus. In the mainland of China, the growing areas of citrus included Hubei, Hunan, Jiangxi, Fujian, Zhejiang,Guangdong,Guangxi, Guizhou, Hainan, He’nan, Jiangsu, Anhui, Chongqing, Shanghai and Gansu province. Many species of pests infest the citrus, and in recent years the loss of citrus production caused by the thrip is increasing, the control strategy used on the thrip is still by spraying the chemical pesticides. With the improvement of the awareness of the health and food safety, the measures by releasing natural enemies and using plant source pest pesticides are becoming popular. In this study, we surveyed the species of the local wild prey mites in the main citrus regions of Hubei firstly. Subsequently, we determined the functional and numerical responses of the commercial predatory mites in the laboratory. Finally, We also evaluated the toxicity of several common pesticides and10kinds of plant extractions on Thrips flavidulus. The major results were as follows:Our field investigations found that the Amblyseius eharai was the dominant species in Zhijiang and Dangyang area, the percentage of A. eharai was83.3%and76.7%respectively. And the Euseius nicholsi was the dominant one in Danjiangkou and HuaZhong Agriculture University, with the percentage reached80%and66.7%respectively. In ZiGui, Yiling and Yidu area, the percentage of the two species above were both high which indicated they were both the dominant species.The functional response showed that the number of T. flavidulus predated by Amblyseius cucumeris was more than that by Amblyseius barkeri and E. nicholsi under the same initial prey densities. However, when T. flavidulus was supplied with the low densities and high densities, similar number of T. flavidulus was predated by the three species of predatory mites. The numerical response results suggested that the prey density significantly influenced the reproductive ability of A. cucumeris and E. nicholsi, but not on A. barkeri.The toxicity bioassay of9kinds of pesticides revealed Chlorpyrifos presented the highest virulence to the T. flavidulus’s adult and nymph, the LC50was0.7214mg/L and0.6922mg/L respectively. Abamectin also showed the lethal effects to adult and nymph of T.flavidulus, the LC50was0.9687mg/L and0.9909mg/L respectively. The field control effects indicated the best period for preventing the occurrence of T. flavidulus was flowering and after flowering. In the several tested pesticides, our results suggested the abamectin, as the biogenic pesticides, could be used major pesticides in practice. We also provided the evidence that nicotine extractions represented the strongest poisonousness to the adult and nymph of T. flavidulus, and the next was Veratrum nigrum and Sophora flavescens extractions.