The Effects Of Fenoxycarb On The Development And Immunity Of Tenebrio Molitor

Fenoxycarb (FC), a carbamate, is one of synthetic juvenile hormone analogues which are used as pesticides. Its structure does not bear much similarity to that of juvenile hormone, but possess analogical function compared with biological activity of juvenile hormone. One of the important storage pest, Tenebrio molitor (Coleoptera: Tenebrionidae), was treated as as the research object in this paper. The contents of this research were focused on the effects of FC on the development and immunity of T.molitor treated with FC by the method of surface dropping.Six levels of concentrations of FC dissolved in acetone were made to treat T.molitor ,such as 0.01,0.1,1,10,100 and 1000ng/μl. Through the method of surface dropping, its effects on the development of T.molitor were observed and determined on the weight gain, development duration, mortality, pupation rate, eclosion rate, the female rate, overage rates, malformation rates. In addition, three levels of concentrations of FC dissolved in acetone were made to treat T.molitor, such as 10,100 and 1000ng/μl. Through the method of surface dropping, its effects on the immunity of T.molitor. The larvae treated with FC were incubated for 20h before they were stimulated by injecting 1×106 /ml E.coli DH5α,then its hemolymph were collected respectively at the following interval, such as 0h and 4h, 8h, 20h, 24h, 48h, 72 h, 96 h, 120 h, 144 h and 168h. At the same times the activities of phenoloxidase (PO), lysozyme (LSZ), nitric oxide synthase (NOS) were determined as humoral immunity indicators, as well as the cellular immunity indicators, such as total haemocyte count (THC), the number of nodulation and the rate of hemocyte-spreading, the purpose was to assess the effect of FC on the immunity of T.molitor. Moreover, indoor experiments were made to testify the effects on the mortality of T.molitor by using mixture of FC and Bacillus thuringiensis (Bt). The results showed that FC could prolong the larval stage, increase its mortality, suppress larval metamorphosis and pupal emergence, induce supernumerary larval, cause malformation of pupae and adults as well. With the increasing of FC concentration, the repressive effects on the development of T.molitor became much more obvious. For example, the pupation rate, eclosion rate and female pupae rate were significantly decreased, and overage and malformation were observed obviously with 10ng/μl FC. The mortality rates of T.molitor were significantly increased when it was treated with 100ng/μl FC. The rates of pupation and emergence decreased significantly with the increase in FC concentration. The indoor experiments also approved that FC can suppress the immune defense effectively to exogenous bacteria. After stimulating with E.coli DH5α, the PO, LSZ, NOS activity were significantly lower than those of the positive control group. The THC, number of nodulation and the rate of hemocyte-spreading were reduced. Through the teatment by both of FC and Bt, the results showed that the mortality rates of T.molitor could be increased significantly compared with the treatment by Bt only.FC can inhibit significantly the development and immunity of T.molitor, control T.molitor effectively and reduce its damage as well.