Improved techniques for monitoring Dolichogenidea gelechiidivoris (Hymenoptera: Braconidae), an endoparasitoid of Tuta absoluta, in tomato fields

Abstract

The tomato leafminer Tuta absoluta is a major pest threatening global tomato production, particularly in the Mediterranean basin. Biological control strategies using predators and parasitoids, such as the braconid parasitoid, Dolichogenidea gelechiidivoris, have been developed, yet efficient field sampling methods for D. gelechiidivoris are lacking. This study evaluates improved monitoring techniques, including yellow sticky traps (YSTs) and laboratory-based detection methods, to enhance parasitoid assessment. Field trials in commercial tomato greenhouses revealed no significant correlation between parasitoid captures on YSTs and actual parasitism rates, limiting their reliability for decision-making in IPM. In contrast, two laboratory techniques—sodium hypochlorite and sodium chloride dissections—significantly improved detection efficiency (~ 83%) compared to conventional methods based on adult emergence from tomato leaflets galleries collected from the field (~ 45%). Additionally, these techniques reduced detection time from 2-3 weeks to a few hours, providing a rapid and accurate identification of parasitized larvae. Thermal treatment and lactic acid methods showed limited effectiveness, with lactic acid completely failing at early parasitism stages and thermal treatment unable to distinguish parasitized larvae. These findings highlight the importance of optimized sampling techniques to enhance T. absoluta IPM strategies and underscore the limitations of YSTs for parasitoid monitoring. The proposed dissection-based methodologies represent a major advancement, facilitating timely decision-making in biological control strategies. Moreover, these methods contribute to the conservation of D. gelechiidivoris by improving detection accuracy and enabling targeted parasitoid management in tomato crops.