Age-specific Functional Response of Trichogramma brassicae (Hymenoptera: Trichogrammatidae) Parasitizing Different Egg Densities of Ephestia kuehniella (Lepidoptera: Pyralidae)

Abstract

The parasitoid Trichogramma brassicae Bezdenko is used for inundative releases in biological control programs against lepidopteran pests in agro-ecosystems. Age-specific functional responses of T. brassicae to different egg densities (5, 10, 20, 30, 40, 60, and 80) of sterilized eggs of Ephestia kuehniella at 23±1°C, 60±5% RH, and 16:8 h (L:D photoperiod ) were studied. E. kuehniella densities were separately presented to a single mated female of T. brassicae (1-day-old). The egg densities were replaced every day until the parasitoid died and each density was replicated 20 times. A type III functional response was obtained for the one-day-old females and a type II for two- to nine-day-old ones. Results show that parasitoid age influences searching efficiency and handling time. Searching efficiency (a´) varied as adult parasitoids aged. In contrast, handling time increased with age. The lowest and highest values were obtained in days 1 and 9 of the parasitoid's life, respectively. The maximum rate of parasitism (T/Th) decreased significantly with an increase in parasitoid age. It was concluded that T. brassicae females were most efficient at early ages of their life and might be capable of efficiently suppressing lepidopteran pest populations. Keywords: Age-specific parasitism, Biological control, Host density, Parasitoid, Search rate