Effect of emergence time on some biological aspects of Trichogramma evanescens (Westwood) (Hymenoptera: Trichogrammatidae)

Abstract

Trichogramma species are minute endoparasitoids of insect eggs that are considered one of the most efficient natural enemies due to their vital role against lepidopteran pests. This experiment was achieved to evaluate the effect of the emergence time of T. evanescens (Westwood) on the emergence rate, % females, % males, sex ratio, longevity, and the emergence of first generation (F1). Mass rearing of Sitotroga cerealella and T. evanecsens was performed and the previous parameters were investigated throughout an emergence period extended to 16 hrs. The emergence time has a clear impact on the tested biological parameters. The highest values of % emergence of T. evanecsens was obtained at the 7th hrs of emergence. The female percentage increased gradually to achieve the highest rate (63.58%) at the 3rd hrs, then it declined gradually to record the lowest rate (50.00%) at the 15th hrs and 16th hrs of emergence. A significant decrease in the female numbers was started after 8th hrs. There were significant negative correlations between the emerging time and each of emergence percentages and the % female. There was a negative correlation between the emerging time and longevity of T. evanescens. The longevity was 3.06 days for the parasitoid wasp adults emerged at the 1st hr and enhanced to be 3.19 days at the 3rd hrs. Also, there was a negative correlation between the emerging time and the emerging percentages of F1. Finally, the impact of developmental time on the fitness of female wasps proposes that the high quality of T. evanescens could be enlarged by enhancing the percentage of the individuals emerging early at the 7th hrs of emergence.