Functional response of Trichogramma evanescens parasitizing tomato leaf miner, Tuta absoluta on three tomato varieties.
The egg parasitoid, Trichogramma evanescens Westwood, is used for inundative releases in biological control programs against the tomato leaf miner, Tuta absoluta Meyrick, in agro-ecosystems. One of the most important host-parasitoid interactions is functional response that its type and parameters are affected by different factors including host plant characteristics. In this research, functional response of T. evanescens to different egg densities (2, 4, 8, 16, 32, and 64) of T. absoluta was investigated in a growth chamber (26±2°C, 50±10% RH, and 16:8 hours L:D photoperiod), on three varieties of tomato (Mobil, Riogrande, and Early Urbana-703). Type of functional response was determined by logistic regression and its parameters, i.e. searching efficiency and handling time, were calculated by nonlinear regression model using SAS software. Functional response of this parasitoid was type III on Mobil and Riogrande and type II on Early Urbana-703. Searching efficiency (a) for each host density was 0.0368, 0.0736, 0.1472, 0.2944, 0.5888, and 1.1776 on Mobil, and 0.0374, 0.0748, 0.1469, 0.2992, 0.5984, and 1.1968 h-1 on Riogrande varieties, respectively. Also, on Early Urbana-703, the attack rate was 0.1045 h-1. The handling time was 1.0276, 1.1017, and 1.3289 hours with maximum parasitism of 23.3, 21.7, and 18.06 eggs on these varieties, respectively. It is suggested that physical structure of Early Urbana-703 variety may interfere with the parasitoid's performance, resulting in an impaired searching efficiency and parasitism ability. Some applied aspects of the findings are discussed.