Biological characteristics and parasitization potential of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) on the whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae), a pest of greenhouse crops in north-western Indian Himalayas

Abstract

Abstract Background The greenhouse whitefly, Trialeurodes vaporariorum Westwood (Hemiptera: Aleyrodidae) constitutes key pests of greenhouses and field crops, which have developed pesticide resistance over the years. It has emerged as a difficult pest to manage owing to its indiscriminate exposure to higher dosages of insecticides. The use of natural enemies is environmentally safe alternative management tactic. Efficacy of Encarsia formosa Gahan (Hymenoptera: Aphelinidae) was determined by studying its biological characteristics on T. vaporariorum. Results Parasitization by E. formosa was higher on fourth-instar nymphs of the greenhouse whitefly (GHWF) (37.2%), which was at par with that of third instar (36.4%), both differing significantly to the parasitization observed in second instar (19.6%). Total developmental duration of the parasitoid was longer on second instar (33.2 days) than that of fourth instar (29.9 days). Adult longevity was found significantly higher for the adults that emerged from fourth-instar nymphs of GHWF, which was at par to that of third instar and longevity of E. formosa adults was significantly higher in the absence of parasitoid host. The size of parasitoid that emerged from different instars of GHWF varied non-significantly. T. vaporariorum was reared on brinjal, cucumber, French bean, lettuce, tobacco, and tomato plants for mass production of E. formosa. Among them, French bean and tobacco were found to be the best host plants for mass production of E. formosa based on higher parasitization (37.2%). Total developmental period varied from 26.4 to 27.3 days on different host plants, the variations being non-significant. The maximum adult longevity was observed on cucumber (8.0 days) in the absence of host, and the adult size of parasitoid varied non-significantly. Results on host to parasitoid ratio of 5:1, 10:1, 20:1, 40:1 and 80:1 revealed that parasitization rate varied from 61.2 to 95.0% with maximum parasitization recorded in host–parasitoid proportion of 20:1 and minimum in 80:1. The total developmental duration varied non-significantly among all the proportions (15.1–15.4 days). Adult longevity was higher in the proportion of 40:1 (6.5 days), which was at par to the proportion of 5:1 (6.2 days), 20:1 (6.2 days), 80:1 (6.2 days) and 10:1 (6.1 days) in the absence of the host, respectively. Conclusion This study suggests that augmentative biological control of T. vaporariorum under polyhouse conditions with E. formosa appears to be an effective strategy for the management of this economic pest.