| To provide the basis for the coordinated use of parasitic wasps and microbial pesticides for pest control, we used Empedobacter brevis, Meteorus pulchricornis and two lepidopteron pests Spodoptera litura and Mythimna separate, conducting a series of experiments about the toxicity of E. brevis to different hosts, parasitization selection of the host larva infected with bacteria in different spore concentrations and infection time, pathogen transmission experiment, selection behavior between healthy larvae and infected larvae, and combine control of S. litura with M. pulchricornis and E. brevis. The main results are as follows:1. Parasitization of the host infected with bacteria and pathogen transmission in the parasitoid M. pulchricornisIn order to assess parasitism rate of M. pulchricornis on S. litura larvae infected with E. brevis in different concentrations and infection tome, the test set three concentrations of E. brevis(5.00×107、1.25×107、3.13×106spores/mL)and by various days (1-5days) after the infection. The results showed that the parasitism rate of M. pulchricornis on infected host larvae was low (10%-20%). The parasitism rate increased and then declined with time post infection in a quadratic cure, which was higher at the time of2and3days post infection than the other times. The final experiment on pathogen transmission was performed by exposing either of S. litura or M. separate larvae that were infected with the bacteria to parasitism after various days after the infection, and then healthy hosts to the parasitoid. The result showed that the parasitoid can transmit the pathogen through parasitization, and the transmission success decreased with the time post infection. The results of this study suggested that M. pulchricornis may attack host larvae infected with the bacteria E. brevis in a low rate, and might transmit the pathogen through parasitization of infected hosts.2. Parasitization selection for pathogen-infected host in the parasitoid M. pulchricornisIn order to investigate the parasitization selection of infected host in the parasitoid, first we used indoor cover cage test to simulate field conditions, did the non-choice and choice test compare the selection of parasitoid to the infected host and the healthy host, including the time of first into host plaque, the number of select parasitic and larvae parasitized. The results showed that in non-choice test, the parasitic wasp for the first time within the30minutes into the plaque was no significant difference between the first acupuncture, parasitic wasps acupuncture susceptible host more often than healthy host, but no significant difference between the two (P=0.78) the last parasitic larvae, healthy host is the number of parasites is greater than the susceptible host, there was no significant difference between the two (P=0.34). And in choice test, in30min the parasitoid for the first time into the plaque was no significant difference between the first acupuncture. First select the number of healthy host plaque than a sense of disease host plaque, but there was no significant difference (P=0.44), the number of acupuncture health-host more susceptible host, but no significant difference between the two (P-0.21), in the last number of parasitic larvae, healthy host is greater than the number of parasites susceptible host, there was a significant difference (P=0.04) between the two.Under indoor condition, we did choice test compare the selection of parasitoid to the infected host with different infection time. The trial was conducted in dual-choice method in which host larvae of1-day infection were exposed to parasitism together with hosts of other times. The results showed that the parasitoid preferred the host of1-day infection to that of3-day or4-day infection.3. Integrated effects on S. litura larvae of M. pulchricornis and E. brevisTo assess effects of the parasitoid-host ratio and the bacteria E. brevis on S. litura larvae mortality and parasitism rate, two factors each with three treatment levels were manipulated, including3wasp-to-host ratios (0,1:20and1:10) and3concentrations of the pathogen solution (0,5.00×107spores/mL and1.25×107spores/mL).The results showed that parasitoid-host ratios and bacteria concentrations not only have a significant impact on the mortality rate independently and in interaction. Under the same host-to-wasp ratio, host mortality increased with bacterial concentrations, but the increasing extent varied among the concentrations. The ratio of wasps to hosts influenced parasitism rate, which was higher with1:10than1:20, but bacterial concentrations did have influence parasitism rate. |
PDF Full Text Request