Evaluation of comparative parasitic efficiency and biology of hymenopteran egg parasitoids, Trichogramma chilonis and T. japonicum on Corcyra cephalonica and Helicoverpa armigera

Abstract

Aim: To evaluate the comparative parasitic efficiency and biology of Trichogrammatid wasps on noble laboratory host Corcyra cephalonica as well as on Helicoverpa armigera, the cosmopolitan, polyphagous and precarious insect pest of many cultivated crops. Methodology: The biology of Trichogramma chilonis and T. japonicum, their sex ratio, and parasitic efficiency were studied. Host insects were reared on artificial diet to obtain their eggs for initiating the experiment. Egg-card pieces were prepared with the irradiated eggs of respective host insects. Egg-cards were introduced into the tubes containing freshly emerged adult parasitoids. Parasitized egg-cards (Trichocards) were kept separately in plastic tube to study the biological attributes and percent parasitization of the parasitoids. Egg cards of different host eggs taking eggs of different age groups were prepared to study the effect of age of host eggs on the biological efficiency of the parasitoids. Results: Irrespective of Trichogramma species, the duration (d) of eggs to adult period was more when reared on the eggs of H. armigera than on the eggs of C. cephalonica. Maximum life stage duration of T. chilonis and T. japonicum from egg to adult was 8.2 days and 10.2 days, respectively, when reared on H. armigera eggs. There was maximum parasitization (84.8%) of fresh eggs of C. cephalonica by T. chilonis as compared to the egg parasitization of 73.4% by T. japonicum. Likewise, extreme parasitization of fresh eggs of H. armigera was recorded as 62.4% when parasitized by T. chilonisas against 59.7% parasitization by T. japonicum. Interpretation: According to the study, H. armigera eggs have the finest biological and parasitic features in terms of the highest adult longevity, sex ratio, mean progeny female-1, and mean adult egg-1, making them the best for mass production of the egg parasitoids, T. chilonis. Key words: Corcyra cephalonica, Host eggs, Helicoverpa armigera, Parasitization, Trichogramma