Reproductive performance of Trichomalopsis uziae as influenced by density of its female and host (Exorista bombycis) with a note on host exposure duration for parasitism

Abstract

Trichomalopsis uziae Sureshan and Narendra Kumar (Hymenoptera: Pteromalidae) is a new addition to the already reported parasitoid complex of the tachinid uzi fly, Exorista bombycis (Diptera: Tachinidae), which causes 10-20% reduction to the silkworm (Bombyx mori L.) cocoon production in the states of Karnataka, Andhra Pradesh, and Tamil Nadu. Due to the non-availability of information on its biological characteristics, an attempt has been made in the present investigation to document the parasitism impact of T. uziae female at various densities of its host and reproductive performance of parasitoid at ratios of 1 to 5:5 (Parasitoid: Host) and 1:1 to 50 (P: H). The reproductive performance of the parasitoid was also assessed based on the durations of host exposure for 1 to10 days at a constant P:H ratio of 1:5. The results revealed that there was no perceptible change in the rate of parasitism at different parasitoid densities. However, the progeny production per female was significantly higher (P < 0.01) at a P:H ratio of 1:5 in comparison with 2:5 to 5:5. Further, at a variable host density (from 1 to 50), there was a linear decrease in per cent parasitism with an increase in host density and it was more drastic from a host density in exceed from 15. However, both progeny production and sex ratio increased with an increase in host density, more so from a host density upwards of 15. The host exposure duration and parasitism rate were significantly inferior at 1day exposure, while it was considerably high at other exposure periods. The progeny production was significantly higher at 2 to 5 days of exposure period without much difference in the sex-ratio.