Efficacy of Trichogramma evanescens and Bacillus thuringiensis var. kurstaki in control of Cydia pomonella (L.) in Turkey

This study was conducted to evaluate the effectiveness of Trichogramma evanescens Westwood (Hymenoptera: Trichogrammatidae) release with as well as without Bacillus thuringiensis var. kurstaki (Berliner) in biological control of Cydia pomonella (L.) (Lepidoptera: Tortricidae) in the Galaxy Gala apple variety grafted onto M9 rootstock in 2016. Four treatments were analyzed: releasing T. evanescens alone (TE), applying B. thuringiensis var. kurstaki (BT) alone, applying both (TE + BT), and a control (C) without any application at all. The experiment design entailed randomized blocks with four replicates. In each generation of the egg stage, 100,000 parasitoids per hectare were released twice (1440 parasitoids/plot), with an interval of 7-10 days. In the larval stage, BT was applied twice for the first generation and once for the second. Weekly counts were performed regularly. The decrease in egg count was 52.15% in TE, 58.99% in BT, and 65.46% in TE + BT plots. The decrease observed in larval numbers was 68%, 73.33%, and 94.66%, respectively. Egg parasitization rates varied between 58.64% and 69.79%. At harvest, fruit infestation rates were 9.66% and 8.33% in TE and BT plots and just 2.0% in the TE + BT plot, versus 34% in the control plot. Promising results were achieved in biological control of C. pomonella when TE was combined with BT. The combined treatment of both biological control agents significantly decreased the population of the pests and crop damage. The natural enemy alone was not effective in keeping the population below the economic threshold level.