›› 1997, Vol. 40 ›› Issue (-1): 165-171.

• RESEARCH PAPERS • Previous Articles     Next Articles

IMPACT OF SEVERAL INSECTICIDES ON THE PREDATION FUNCTION OF PIRATA SUBPIRATICUS

Wu Jincai Xu Jianxiang Li Guosheng Cheng Xianian Yong Deben   

  • Online:1997-12-20 Published:1997-12-20

Abstract: So far main evaluating method about effect of pesticides on natural enemies has been concentrated on their lethal rate resulted and rarely on their predation function. Impacts of three insecticides, shachong-shuang, methanidophos and buprofezin on the predation function of Pirata subpiraticus on brown planthopper were studied in this TR paper. Decrease rate of predation function, FD= [∑(Dt+St×FDt,)] /TR×100 wast=l proposed as comprehensive evaluation of impact of insecticides to natural enemies,where Dt=death rate of natural enemy at t time, St=survival rate of natural enemy at ttime, FDt=decrease rate of predation function at t time and TR=duration of predation function recovery. The experimental results showed that 540 mg/L and 810 mg/L of shachong-shuang caused low death rates to the wolf spider, which are 12.63% and 27.57%, respectively, but had a great impact on its predtion function, which decreased65.41% and 81.3%, respectively, 100mg/L of methanidophos treatment showed 49.8% of death rate and 68.56% in the decrease of function. These two insecticides showed different affecting machanisms, the later had higher lethal toxicity and shorter duration of predation function recovery. For the third insecticide, buprofezin, both thelethal effect and function decrease of the spider could be ignored. The function recovery of the wolf spider needed about 7 d after shachong-shuan and me-thanidophos treatments. Moreover, the result of field experiment indicated that application of methanidophos would cause resurgence of planthoppers due to the decline of the function of natural enemies.

Key words: shachong-shuan, methanidophos, Pirata subpiraticus, predation func- tion, Nilaparvata lugens