Impact of Trichogramma parasitoid age on the outcome of multiparasitism in the factitious host eggs of Chinese oak silkworm, Antheraea pernyi.

The age of Trichogramma parasitoids could influence biological traits which are of great importance for effectiveness of mass rearing systems. Recent studies demonstrated that Trichogramma ostriniae (TO) could parasitize Antheraea pernyi eggs through multiparasitism along with other Trichogramma species, although few adults could emerge successfully. It is important to characterize the factors modulating the performance of TO on A. pernyi eggs, notably in order to try enhancing its quantitative emergence through multiparasitism for further use in biological control. In this context, irrespective of host age, we tested different ages of TO females (from 0.5-day- to 6-day-old postemergence) in multiparasitism with Trichogramma chilonis (TC) on A. pernyi eggs. The results of the present study confirmed that TO parasitism on A. pernyi eggs was largely age dependent. Higher percentage of multiparasitism and higher number of emerged TO adults were recorded in the treatment where 3-day-old TO females were used for parasitization with TC on A. pernyi host. In addition, we also tested different female ratios of both Trichogramma species to find out an optimal ratio for use in mass production. The highest percentage of multiparasitism, emergence and optimum emerged number of TO (per A. pernyi egg) was observed with the ratio 3:2 (TO:TC) per 1 host egg. This study demonstrated that the age of TO females can significantly affect their performance in multiparasitism of large A. pernyi eggs. These results prompt for more research in order to develop an effective multiparasitism-based production of TO at the industrial scale. [ABSTRACT FROM AUTHOR]