Multi-parasitism: a promising approach to simultaneously produce Trichogramma chilonis and T. dendrolimi on eggsof Antheraea pernyi

Abstract

Ostrinia furnacalis is considered the main insect pest on maize throughout Asia and both Trichogramma dendrolimi and T. chilonis are the major species used for control in Northeast China. However, the suboptimal control effect of T. dendrolimi (requiring releasing high numbers of parasitoids), as well as the suboptimal production efficiency of T. chilonis in mass-rearing facilities, have reduced to some extent their application. Given these challenges, we evaluated under laboratory conditions the possibility of simultaneously producing T. dendrolimi and T. chilonis on Antheraea pernyi eggs using multi-parasitism at different ratios (T. dendrolimi: T. chilonis: fresh A. pernyi eggs = 1:4.7:70, 1:3.5:70, 1:2.8:70, and 1:2.3:70). Our data showed that T. dendrolimi and T. chilonis could be successfully co-produced on A. pernyi eggs. The parasitism rate and the number of emerged parasitoids per egg were significantly higher in multi-parasitism than in mono-parasitism conditions whereas the emergence rate (> 92%) and the number of female remained constant; suggesting a high host quality. When the parasitoids: hosts ratio increased, all these biological parameters decreased significantly whereas the emergence rate was still constant. A two years of field experiments enabling to evaluate the ability of the parasitoids produced from mono- and multi-parasitized wasps to control O. furnacalis, demonstrated that the control of the pest population was higher when parasitoids were produced under multi-parasitism than under mono-parasitism conditions (83% vs. 68%, respectively). The results of this study provided useful information for a more effective and economical method of controlling O. furnacalis and developing Trichogramma products using multi-parasitism.