Effect of Rare, Locally Isolated Entomopathogenic Fungi on the Survival of Bactrocera oleae Pupae in Laboratory Soil Conditions

Greece's olive oil production is significantly affected by the olive fruit fly <i>Bactrocera oleae</i> (Diptera: Tephritidae), and its presence is perceived when it is too late to act for damage recovery. In this work, some unexplored entomopathogenic fungi (EPFs) were studied for their efficacy on olive fruit fly pupae in soil samples. Olive grove soil samples were collected to evaluate the effect of EPFs in their natural environment. The parameters that were analyzed to evaluate the performance of EPFs on <i>B. oleae</i> included the adult survival time, pupa hatch time, and the presence of mycelium on <i>B. oleae</i> pupae and dead adults. The efficacy of some EPFs was highlighted by the mycelium present on dead <i>B. oleae</i> adults after treating pupae with fungal isolates on the soil substrate. The results showed that for the soil substrate, external fungal growth was observed in dead adults with <i>A. contaminans</i>, <i>A. keveii</i>, <i>A. flavus P. lilacinum</i>, and <i>T. annesophieae</i> (100%). Remarkably, the lowest male proportion for soil and non-soil substrates was for <i>A.</i> flavus (0.41-0.42) for the first time, for <i>A. keveii</i> (0.36), and for <i>P. citreosulfuratum</i> (0.41) on the soil-only substrate in contrast to the control treatment (0.5 for both substrates). Given the high infestation caused by the olive fruit flies in Greece, the results of the study emphasize to use of incorporating certain EPF-based biopesticides into integrated pest management (IPM) programs.