The Effects Of Two Ascovirus Isolates To The Developmental Fitness Of Three Armyworm Larvae

At present, the biological pesticides are becoming more and more important in pest and disease integrated control. However, there is little biological pesticide which can be applied to practical production. Among biological pesticides, the insect viruses are significant resources of biological control. The ascovirus is a kind of insect virus with biological control potentiality. As it is newly discovered, there is a lack of basic research on the discussion of its biological control potentiality. The thesis takes the Heliothis virescens ascovirus 3h isolate and Spodoptera frugiperda ascovirus isolate 84-36 as the main objective. It studies the affect on development fitness of Spodoptera exigua, Spodoptera litura and Helicoverpa armigera caused by the two ascoviruses strains from seven aspects, like fatality rate of different concentrations. Meanwhile, it compares the pathogenicity of these two strains to the same host larvae. The main research achievements are as follows.1?The comparison of the affect of two ascovirus isolates to the developmental fitness of S. exigua larvaeBy comparison, the HvAV-3h isolate and 84-36 isolate has the exactly same fatality rate in different concentration. In the same time, the S. exigua larvae infected with HvAV-3h isolate has prominently shorter developmental duration than the one infected with 84-36 isolate. Per oral infection, the HvAV-3h isolate can infect all S. exigua larvae, while only the 1st-3rd instar larvae be orally infected by the 84-36 isolate. When infected by injection, the weight, daily food consumption and gross consumption of larvae affected by HvAV-3h isolate is prominently lower than affected by 84-36 isolate. Consequently, from the perspective of biological control potentiality on beet armyworm, HvAV-3h isolate has better development potential than 84-36 isolate.2?The comparison of the affect of two ascovirus isolates to the developmental fitness of S. litura larvaeThe HvAV-3h isolate and 84-36 isolate has the same fatality rate in different concentration. In the meantime, the S. litura larvae infected with HvAV-3h isolate has prominently shorter developmental duration than the one infected with 84-36 isolate. Per oral infection, the HvAV-3h isolate can infect the 1st-2nd instar larvae, while the 3rd-5th instar larvae be orally infected by the 84-36 isolate. When infected by injection, the weight, daily food consumption and gross consumption of larvae affected by HvAV-3h isolate is prominently lower than affected by 84-36 isolate. Consequently, from the perspective of biological control potentiality on beet armyworm, HvAV-3h isolate has better development potential than 84-36 isolate.3?The comparison of the affect of two ascovirus isolates to the developmental fitness of H. armigera larvaeHvAV-3h isolate has greater fatality than 84-36 isolate in different concentration. Per oral infection, HvAV-3h isolate can infect H. armigera larvae in the ist-2nd instar, while 84-36 isolate fails to infect larvae. After injection inoculation, the developmental duration of H. armigera larva affected with HvAV-3h isolate is obviously shorter than affected by 84-36 isolate and die. Meanwhile, the weight, daily food consumption and gross consumption of Helicoverpa armigera larva affected with HvAV-3h isolate is obviously less than affected by 84-36 isolate. Therefore, from the aspect of biological control potential on H. armigera, HvAV-3h isolate has better development potential than 84-36 isolate.In conclusion, by analyzing the affect on development fitness of the three armyworm larvae caused by the two ascovirus isolates, it is discovered that Heliothis virescens ascovirus 3h isolate has great biological control developmental potential on armyworm larvae.