Superparasitism inTrichogramma Evanescens minutum riley (Hymenoptera: Trichogrammatidae), an egg parasite of sugarcane and maize borers in India

Summary

1. There are two diametrically opposite schools of thought as to the utility ofTrichogramma evanescens minutum Riley for the biological control of insect pests.

2. Experiments have been conducted to assess the role of superparasitism inTrichogramma field colonisation.

3. The observations from the experiments show that as a result of superparasitism, though, one to three adult parasites may emerge from the egg ofCorcyra cephalonica (Staint.), they are defective; they generally have ill-developed wings and are inactive. They mate with forms of about their own size only, if they show any tendency to mate at all; and even if they mate the fecundity is comparatively low.

4. The reason for the improper development of the parasites is attributed to the sharing of the limited amount of food in the host egg between the developing parasites.

5. These observations lead the authors to the conclusion that superparasitism is a very potent factor that determines the success or failure of the colonisation ofTrichogramma in the field.

6. For successful colonisation, it is suggested that when the parasites are reared in the laboratory for mass liberation, every care should be taken to avoid superparasitism of the host eggs, for which special techniques have to be evolved; and also the initial population of the borer eggs in the field has to be taken into consideration at the time of the release.