INFLUENCES OF HOST PLANTS ON THE FUNCTIONAL RESPONSE OF TRICHOGRAMMA CHILONIS (ISHII), A PARASITOID OF HELICOVERPA ARMIGERA (HUBNER)

Helicoverpa armigera (Hubner) (Lepidoptera: Noctuidae), is a polyphagous pest that damages a wide range of crops worldwide. In India, although its incidence is reported for over 200 plant species, it severely reduces productivity in chickpea (Cicer arietinum L.), and tomato (Lycopersicum esculentum L.), crops. One of the most effective natural enemies reported for its biological control is Trichogramma chilonis (Ishii), which attacks the eggs of H. armigera. In general, behavioural responses influence parasitoids’ ability to control host pests. The functional response i.e., response of a parasitoid to its hosts’ egg density can be considered one of them. It may be affected by several abiotic and biotic factors including host plants. However, how the functional response of T. chilonis is influenced by host plants is still unknown. In the present study, we attempted to evaluate the influences of host plants (chickpea and tomato) on the functional response of T. chilonis at H. armigera’s eight different egg densities (2, 5, 10, 20, 30, 40, 60 and 80 eggs/female/day) under laboratory conditions. For all host plants, the logistic regression revealed a type-II functional response. The attack rate (a) of T. chilonis was observed to be 0.0463±0.0038 and 0.0623 ±0.0058 per hour with estimated handling times (Th) of 0.4256 ±0.0432, and 0.7245±0.0537 hour for chickpea and tomato, respectively. Although the functional response features, particularly with regard to parasitism, did not vary significantly among host plants (at a 95% confidence interval), the T. chilonis females, however, had a grater effectiveness against H. armigera eggs on chickpea. The findings of this study provide new insights into hostparasitoid interactions.