The Intraguild Predation In The Phytoseiid Mites Exotic Amblyseius Swirskii And Indigenous Neoseiulus Barkeri(Hughes)

The phytoseiid mites of exotic Amblyseius swirskii and indigenous Neoseiulus barkeri are generalists which used in biological control of Bemisia tabaci(Gennidius) Frankliniella occidentalis (Pergande), Tetranychus truncatus, Trialeurodes vaporariorum(Westwood) and other pests. The thesis studied the intraguild predation between exotic Amblyseius swirskii and indigenous Neoseiulus barkeri in a series of experiments under laboratory conditions. The female aggressiveness (quantified as attack probability) in intraguild predation on larvae was evaluated in order to determine intraguild predaor and intraguild prey. Moreover, the density dependent effects of 4 species of extraguild prey on intraguild predation were observed. Furthermore, the predation preference of intraguild predator between intraguild prey and extraguild prey with different density were evaluated. Finally, the risk of Amblyseius swirskii to local species was assessed by Cox regression analysis model in order to establish a reasonable combination of different natural enemies in biological control. The main results are as follows:1. By Kaplan-Meier survival analysis, the female aggressiveness (quantified as attack probability) in intraguild predation on larvae was evaluated that A. swirskii was more aggressive against heterospecific larvae than N.barkeri in intraguild predation(Breslow tests: X=8.42; df=1;P=0.004). Therefore, A.swirskii is IG-predator and whereas N.barkeri is IG-prey in intraguild predation between A. swirskii and N. barkeri.2. IGP between A.swirskii and N.barkeri in the absence or presence of four species of shared Extra-prey was studied to evaluate the effects of three different densities of Extra-prey (no Extra-prey, insufficient Extra-prey and sufficient Extra-prey) on IGP, respectively. The density of any kind of Extra-prey had significant effects on IGP showing the predation rate of IG-predator in IGP decreased whereas the oviposition rate and survival rate increased gradually with the increase of density of Extra-prey. The predation rate of IG-predator was the highest whereas the oviposition rate and survival rate is the lowest in the absence of Extra-prey. Meanwhile, the predation rate of IG-predator was becoming lower whereas the oviposition rate and survival rate higher in the presence of Extra-prey. Therefore, IGP was reduced in the presence of four different species of Extra-prey and thus resulted in possibly feasible releasing two phytoseiid mites together to control any species of Extra-prey.3. The results of IG-predator preference for IG-prey or Extra-prey with different densities showed that IG-predaor A. swirskii mostly preferred preying on the Extra-prey to any speices of IG-prey(Breslow tests:all P’s＜0.05). The preference of IG-predaor for Extra-prey is in a order of the larvae of T. Truncatus,1st larvae of B. Tabaci,1st larvae of T. Vaporariorum and then 1st larvae of F. occidentalis(F3,68=4.185,P=0.009).4. The results from the Cox regression model showed that the exotic phytoseiid mite A. swirskii with the regression coefficient of 1.249 had threat to the indigenous phytoseiid mite N. barkeri,and resulted in that the survival time of N. barkeri decreased in the presence of A. swirskii. Meanwhile, N. barkeri with the regression coefficient of -0.911 had no threat to A. swirskii.