Studies On Predation Abilites And Application Of Amblyseius Eharai

As the abuse of pesticide and the loss of predators, the number of spider mites is out of control and the resistance of them to pesticides is increasing. Recently, the biological control through the use of natural enemies has been an important treatment in controlling citrus orchards. As one of the most abundant species in the citrus orchards, Amblyseius eharai Amitai et Swirski is widely distributed in our country and it can live on many different kinds of plants. It has been the most important predator mites in controlling pest mites. In this study we investigated the following aspects of A. eharai:1) the predation ability,2) the toxicity to A. eharai of common chemical pesticides,3) the effect of the release rate and pollen on A. eharai and4) the effect of ground cover on predator mites. This study will offer the theoretical basis for the protection and the application of A. eharai.The functional response showed that A. eharai had high predation ability on all the three kinds of preys(Panonychus citri (McGregor) and first instar nymph of Thrips hawaiiensis Morgan and Dialeurodes citri Ashm). Temperature influenced the parameters but not the type of functional response. A. eharai got its highest predating ability at28℃. The predation ability of A. eharai decreased at a too high or too low temperature. A. eharai had a preference on P. citri in the presence of P. citri, T. hawaiiensis and D. citri. A. eharai consumed significantly more larvae and nymphs than other stages of P. citri.The toxicity test of pesticides, acaricides and fungicides on A. eharai showed that beta-cypermethrin, Avi pyridaben and prochloraz had high toxicity while buprofezin, propargite, mancozeb and hiodiazole-copper had low toxicity to this predatory mite. Generally fungicides had lower toxicity than pesticides and acaricides.The experiment about release rate of predator mites and the effect of pollen showed that the release rate and pollen affected the biological control greatly. The population density of spider mites could be controlled under the critical value by releasing predator mites with a rate of1:5when the density of P. citri was high and1:10or1:20when the density was low. Pollen played an important role in affecting the population dynamics of A. eharai. Especially with a lack of prey, pollen could be the alternative food source and maintain the population size of A. eharai. Therefore to maintain the survival of predator mites, some treatments like planting grass whose pollen could be a food source should be taken when predator mites are abundant or preys are lacked.The experiment of ground cover management showed that planting grass especially Ageratum conyzoides L. could be beneficial to biological control of P. citri. In the zone of planting grass, the density of P. citri was lower and the density of phytoseiid mites is significantly higher. The planting of A. conyzoides significantly increase the density and the proportion of A. eharai.