Effect of Host Egg Densities on Sex Ratio and Laboratory Performance of Trichogrammatoidea sp. nr. lutea Girault (Trichogrammatidae:Hymenoptera) Collected from Plutella xylostella Linnaus in Kenya.

Four native lines of Trichogrammatoidea sp. nr. lutea Girault collected from Plutella xylostella Linnaus in coastal Kenya were reared on Corcyra cephalonica Sainton (Lepidoptera: Pyralidae) in the laboratory. This experiment was done to explore the possibility for enhancing the potential impact of these native egg parasitoids in terms of favourable sex ratio in the progeny using different host egg densities and competing females during mass production in the laboratory. In addition, other important reproductive parameters such as parasitization success and progeny production were also evaluated. When adult females were placed in-groups of four to oviposit just enough eggs they require to parasitize, the offspring sex ratio was female biased unlike when placed as single females. In group females, host egg patch size (the number of host eggs exposed per adult parasitoid) did not seem to affect the progeny sex ratio, but in test with single females, the offspring sex ratio significantly increased with increasing patch size. Results from this study suggested that placing ovipositing females in groups could be used to maximise percentage of female offspring during mass rearing in the laboratory for field release of T. sp. nr. lutea.

Author(s): Osiemo B. Zipporah*, Gitonga, L.Muthuri, Maranga R.Orangi and Sithanantham, Srinivasan

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