Effect of female vs. male pupa of Scirpophaga excerptalis Walker on reproductive potential of Tetrastichus howardi (Olliff) (Hynenoptera: Eulophidae)

Abstract

Tetrastichus howardi (Olliff) (Eulophidae: Hymenoptera) is gregarious and polyphagous endopupal parasitoid associated with sugarcane stem borers. It is adapted in its host-searching strategy to penetrate tunnels excavated by stem borers which is a prerequisite for a good biological control agent of stem borers. The experiment was conducted at 25 ± 2°C and 65 ± 5% relative humidity in BOD with ten replications at Biological in Division of Crop Protection, ICAR, Lucknow. The number of adult emerged (81.29) from female pupa (81.29) was more than male pupa (65.30). The smaller host pupae (i.e. male pupa) gave rise to small number of parasitoids whereas larger ones (i.e. female pupa) supported development of more parasitoids. The parasitoid completed development in 19.5 days on both pupae. There was no significant difference of development period in male vs. female pupa. The female emergence (%) on female and male pupa was 86.94 and 74.23, respectively. The number and sex ratio of adult progeny emerging from host pupa depends on the size. The large host size is more beneficial to the fitness of daughters than to sons and selection would then favor wasps to lay more daughters in large hosts and more sons in small hosts. It is concluded that parasitoid had high reproductive potential, more female biasesd sex ratio and its gregarious development make possible to multiply on sugarcane top borer in the laboratory.