Winter Survival Of Amblyseius Swirskii And IGP Between It And Two Native Phytoseiidae Species

Amblyseius swirskii (Athias-Henriot)(Acari:Phytoseiidae), native to the eastern and southeastern part of the Mediterranean region, is a generalist predatory mite that feeds on many species of small arthropods. Studies conducted on the biology and predation habit of A.swirskii had shown that it is an efficient biological control agent against whiteflies. It has been commercially available since2005and is widely used to control whiteflies in Europe. Due to the lack of commercialized predatory mites used to control whiteflies in China, we intend to use it to control whiteflies in greenhouse. Before the release of exotic natural enemies, environmental risk assessment should be done. As a part of risk assessment of A. swirskii, here we mainly investigated its establishment potential in Beijing, China, and intraguild predation (IGP) between it and two native Phytoseiidae species, Amblyseius orientalis (Ehara) and Neoseiulus californicus (McGregor).We first calculated the likely annual voltinism in Beijing by combine its thermal budget with local meteorological data, and then did the winter field survival experiments. The results of these two parts alongside thermal biology and cold tolerance of A. swirskii were used to assess its establishment potential in Beijing. A. swirskii could complete a total of20generations per year in Beijing, but it could not to complete one generation between the beginning of November and the end of March.100%mortality was recorded after35days of exposure. Ten vials of A. swirskii were putted in the outdoor every10days from6November2012to25January2013, and the total9treatments were recorded100%mortality when examined in6April2013. Combining experiments results with biological characteristics of A. swirskii, we concluded that A. swirskii is unlikely to establish in Beijing, China.For each pair of species, three experiments were conducted. First, we characterized the levels and symmetry of IGP among the various stages of the predatory mites in the absence of extraguild prey. Second, we investigated IGP in the presence of extraguild prey-Bemisia tabaci (Gennadius). And at last, the development time and preoviposition of both predatory mites when fed on intraguild prey were tested. A.swirskii was the intraguild predator in most combinations where IGP occurred no matter when co-exists with A. orientalis or N. californicus, suggesting it a more aggressive intraguild predator. But, A.swirskii acted as the intraguild predator in70%cases when co-exists with A. orientalis which is slightly higher than that when A.swirskii co-exists with N. californicus (65%). When IGP levels were compared between the presence and the absence of whitefly eggs, for A.swirskii and A. orientalis, significant decreases were observed in only two combinations. In contrast, the IGP levels between A.swirskii and N. californicus decrease significantly in all combinations except for one case. When feeding on intraguild prey, A.swirskii could complete development and reproduction. When fed on A. orientalis eggs, the developmental time of A.swirskii was6.61d, preoviposition was2.37d, and survival rate of immature was as high as100%. When fed on N. californicus eggs and larvae, the developmental time of A.swirskii was6.20d, preoviposition was2.32d, and survival rate of immature was100%. These results suggest there is a higher potential for negative interactions between A.swirskii and A. orientalis than between A.swirskii and N. californicus. We tentatively conclude that introducing A.swirskii may have negative impacts on population of A. orientalis.