The Biological Characteristics And Intraguild Predation Involved By The Phytoseiid Predator Euseius Utilis

The Phytoseiid predator Euseius utilis is a generalist and distributed widespreadly in northern area of China. The life history of E. ulilis reared on five kinds of food was determined in laboratory. Meanwhile, the function response and interference of female adults of E. utilis on Tetranychus truncatus and 1st instar larvae of Frankliniella occidenlalis were measured respectively to evaluate its potential for a biological control agent. Finally, the aggressiveness and con-and heterospecific interaction between E. ulilis and another widely used native species Neoseiulus barkeri were studied in order to assess its risk and establish a reasonably combination of different natural enemies in biological control.1. Development and fecundity of E. ulilis reared on five different kinds of food (leaves&T. truncatus、leaves&Typha pollen、leaves&Pine pollen、leaves&Poplar pollen、 T. truncatus&Typha pollen) showed that E. ulilis could only develop to larvae from eggs in absence of leaves indicating that the presence of leaves played an important role in rearing. The combination of T. truncatus and leaves was mostly suitable for E. ulilis in development and fecundity.2. The functional responses for female adults of E. utilis on T. truncatus and 1st instar larvae of F. occidentalis could be described as Holling II type. E.utilis exhibited higher ability to control larvae and nymph of T. truncatus and Ist instar larvae of E.occidentalis whereas the lowest ability to control adults of T. truncatus. With a fixed number of preys available, the average predation decreased as the predator density increased by mutual competition and interference. E. utilis is promised to be one of the potential biological control agents for T. truncatus and F. occidentalis.3. The inrtaguild predation and cannibalism between E. utilis and N. barkeri showed that the females of both species of predatory mites had difficulties in piercing their eggs and consumed more con-and heterospecific larvae than protonymphs. E. ulitis was more aggressive on conspecific larvae than on heterospecific larvae and the mean predation numbers of E. ulitis on conspecific larvae was higher than on heterospecific larvae in absence of shared food. Hence, E. ulitis was preferentially engaged in cannibalism.The mean predation number of N.barkeri on heterospecific larvae was higher than on conspecific larvae. Therefore, N. barkeri was more probably engaged in inrtaguild predation.