Entomopathogenic Nematodes As Potential Biocontrol Agents Againstbactrocera Oleae(Diptera: Tephritidae)

The olive fruit flyBactrocera oleaeis one of the most serious and economically damaging insects worldwide, affecting the quality and quantity of both olive oil and table olives. Third instar larvae and pupae of several Tephritidae flies were reported to be susceptible to entomopathogenic nematodes (EPNs), but few studies have been carried out on the olive fruit fly. Laboratory assays were conducted to evaluate the susceptibility ofB. oleaelarvae and pupae to two commercial EPN species,Steinernema feltiaeandHeterorhabditis bacteriophoraand two indigenous Italian strains ofH. bacteriophoraandSteinernema carpocapsae. Moreover, an olive assay in the soil was performed to evaluate the capability of EPN strains to enter inside the olive fruits and interact withB. oleaeduring the pupal stage or the emergence of adults in the winter diapause. The susceptibility assays withB. oleaewere performed in well plates, filled with sterile soil (n = 30 for each EPN strain and insect stage). Adult emergence and mortality were recorded daily for 15 days. Dead pupae and adults were dissected to assess nematode infection. The most noteworthy result was obtained withS. feltiaewhich was able to infect more than 80% of larvae and it killed the pupae inside olive fruits and the adults during their emergence with the same efficacy. Since this Tephritidae fly spends several months in the soil, the use of EPNs, in particular,S. feltiaemay represent a promising method to control this pest.