Developmental time, sex ratio and longevity of Amitus fuscipennis MacGown & Nebeker (Hymenoptera: Platygasteridae) on the greenhouse whitefly

Abstract

Amitus fuscipennis MacGown & Nebeker (Hymenoptera: Platygasteridae) is being evaluated as a potential biological control agent of Trialeurodes vaporariorum (Westwood) (Homoptera: Aleyrodidae) on bean crops in Colombia. The life history of this natural enemy is presented in this paper. The developmental time and longevity of fed and unfed adult parasitoids were compared under different temperature and relative humidity combinations. Mean longevity of the parasitoid in absence of hosts was highest (42.2 days) at 15°C and 75 ± 5␛H and lowest (3.9 days) at 15°C and 45 ± 5␛H. Longevity at 25°C and 75 ± 5␛H was also low (10.1 days). A. fuscipennis had the longest mean developmental time (65 days) at 15°C and 75 ± 5␛H and the shortest (23.2 days) at 25°C and 55 ± 5␛H. Combinations of moderate temperature and low relative humidity negatively affected parasitoid longevity. At constant high humidity, an increase of temperature leads to a decrease of longevity. Sex ratio was determined by (a) collecting adults in the field and rearing them to the next generation, (b) exposing different proportions of pairs of parasitoids to whitefly nymphs, and (c) examining the offspring of pairs of parasitoids. Sex ratios of populations collected in the field and reared in the laboratory were strongly female biased. Reproduction of the parasitoid is through thelytokous parthenogenesis. The species carries Wolbachia, the rickettsia that induces thelytoky. Results suggest that A. fuscipennis could be a potentially good biological control agent of T. vaporariorum in environments that are not overly dry or warm