Primary Study On The Mechanism Of Suitability Of Ostrinia Furnacalis Egg To Trichogramma

Trichogramm ostriniae Pang et Chen and T. dendrolimi (Matsumura) are endophagous parasitoids of insect eggs. They are two most important species of parasitoids used in controlling O. furnacalis (Guenee) in China. Results of laboratory studies indicated that O. furnacalis egg was more suitable to T. ostriniae than it was to T.dendrolimi. In this paper, we compared the development of Asian corn borer egg parasitized by the two Trichogramma species, and observed the parasitical behavior of T. dendrolimi on fertilized and unfertilized eggs of O. furnacalis. We also investigated the influence of extracts of wasp on development of corn borer eggs by microinjecting the extract of two wasp species into the eggs of corn borer. Research results are as following.(1)There were no significant differences in the numbers of emergence wasps of T. ostriniae among different host ages, and the emergence rates of wasp for T. ostriniae parasitizing all three host ages were more than85%. Whereas for T. dendrolimi there were significant differences in emergence rate of wasps among different host ages provided. There were significant differences in the amounts of emergence wasps from host parasitized at correspondent age between T. ostriniae and T. dendrolimi.For the eggs parasitized by the T. dendrolimi, as the eggs age increased, the number of eggs developed into corn borer and the number of host egg stoped develping significantly increased, too.(2) The behavior process of T. dendrolimi were same between parasitizing fertilized egg and parasitizing unfertilized egg, but there are significant differences in drilling and ovipositing between parasitizing fertilized eggs and parasitizing unfertilized eggs. The overall time took in parasitizing unfertilized egg was significantly longer than that in parasitizing fertilized egg.(3) There were no significantly differences in parasitim rate by T. dendrolimi between fertilized and unfertilized corn borer eggs, while the emergence rate of wasp on unfertilized eggs was significant higher than that on fertilized eggs. The female sex ratio of T. dendrolimi emerged from unfertilized eggs was significantly lower than from fertilized eggs.(4) Both high concentration extract of whole body and extract of abdominal of T. ostriniae females significantly affected hatchability of corn borer egg, whereas extract from T. dendrolimi female abdomen and the whole body did not. The extract from T. ostriniae could not completely suppress the development of O. furnacalis embryo.