Interactions Among Beauveria Bassiana, Neoseiulus Barkeri And Frankliniella Occidentalis

In order to improve biocontrol effect on single target pest and minimize economic losses, multiplenatural enemies to be integrated has been recommended in the IPM strategy. However, the issue ofbenefits of introducing single or multiple natural enemy species for classical biological control hasbecoming controversial after many years of scientific practice. Since the intraguild predation (IGP),resource competition and antagonism exist among enemies, a better understanding of the interactionsamong multiple natural enemy species would improve their integration into pest management practices.This paper investigated the interactions between Beauveria bassiana and predatory miteNeoseiulus barkeri for the control of their target pest, Frankliniella occidentalis, one of the mostimportant insect pests in ornamentals and vegetables worldwide. Neoseiulus barkeri is distributedwidely and displayed potential for biological control of several species of thrips. Beauveria bassianawas demonstrated potential in managing F. occidentalis. Our study was conducted in laboratory andgreenhouse to evaluate the compatibility between B. bassiana and N. barkeri and the potential use of B.bassiana in combination with N. barkeri for the control of F. occidentalis.1. Interaction between B. bassiana, N. barkeri and F. occidentalisWe screened one of the most virulent strains against F. occidentalis from30new fungal isolates. Thedirect toxicity of different concentration of B. bassiana and the residual toxicity at different time to F.occidentalis were tested. We compared the fungal infection process in the predator and thrips byscanning electron microscopy. The results revealed that B. bassiana successfully infected F. occidentaliswithin60h. In contrast, we never observed penetration of the cuticle of N. barkeri. Neoseiulus barkeridisplayed effective defense against B. bassiana. The ability of conidia carried by N. barkeri and thevitality of conidia were tested, and the results showed that the treated N. barkeri can carry a largenumber of conidia within a short time, the conidia can be dispersed and infected F. occidentalis, andthese synergistic effects were rapidly weakened by the self-grooming behavior of N. barkeri. We alsofound that the preoviposition duration of the female N. barkeri was significantly longer and conidiacould be fed by N. barkeri.2. Interaction among B. bassiana, N. barkeri and F. occidentalisFrom functional response and bioassay experiments, we showed that the predation capability of N.barkeri was not affected by B. bassiana. The first instar larvae of F. occidentalis after having beentreated with the fungus for12h were more vulnerable to be killed by N. barkeri. Second instar larvaeand pupae of F. occidentalis which had been attacked by N. barkeri were more susceptible to B.bassiana infection. When treated the leaves of kidney bean with B. bassiana solution, N. barkeridisplayed behavioral repellence. From two-sex life table study, we found that the life table parameters ofN. barkeri were strongly affected when fed on infected F. occidentalis.3. Application of B. bassiana and N. barkeri for controlling F. occidentalis in greenhouse.We determined the effects of single and combined application of B. bassiana and N. barkeri forcontrolling F. occidentalis in cucumber greenhouse experiments. The results indicated that there were obvious interactions between B. bassiana and N. barkeri with little synergistic effects for F. occidentalisbiological control when combined both simultaneously, so the application of B. bassiana in combinationwith N. barkeri at certain intervals was suggested.