Laboratory and greenhouse endophytic colonization of tomato by three entomopathogenic fungal isolates for the management of Tetranychus urticae and field efficacy trials

Tetranychus urticae is a devastating arthropod in tomato crops, causing significant economic and yield losses globally. Several Metarhizium robertsii and Beauveria bassiana isolates have been extensively tested by direct application against T. urticae. Here, the endophytic colonization of M. robertsii (WG-04 and WG-05) and B. bassiana (WG-11) isolates on tomato plant parts was investigated by different inoculation methods. Their endophytic effect was investigated against T. urticae in the greenhouse and laboratory, and their acaricidal efficacy was evaluated in the field in 2020 and 2021, after their leaf-surface application. At 28 days after inoculation, WG-04 and WG-05 achieved high leaf colonization, reaching 95 % and 100 %, respectively, following foliar application, while WG-11 showed the lowest colonization rate (79 %). The three EPF as endophytes killed 75–94 % of nymphs and 69–85 % of adult females after 4 and 10 days, respectively, in laboratory trials. They also caused a considerable reduction in the establishment of T. urticae life stages on both surfaces of tomato leaves in greenhouse tests. In field trials, their direct application to mites on plants significantly decreased the mite population 8 days after treatment in both experimental years. Overall, WG-05 was the best EPF isolate that deserves further experimentation as an endophyte under field conditions against T. urticae.