The Mediterranean fruit fly, Ceratitis capitata, is a severe pest that has caused significant damage to orchards in northern Iran. Due to its soil-dwelling nature, controlling its population is a challenging task. In this regard, deploying biocontrol agents, such as entomopathogenic nematodes (EPNs), might be an appropriate solution. To assess the biocontrol potential of Iranian strains of two EPN species, Heterorhabditis bacteriophora (Hboj) and Steinernema carpocapsae (Scz), an experiment was conducted utilizing seven concentrations of the nematodes (1.625, 3.125, 6.25, 12.5, 25, 50 and 100 IJs/cm2) against C. capitata larvae in their last instar, which were placed in cylindrical soil containers (4×4 cm). The results revealed that both EPN species were highly effective in controlling fruit fly larvae, with S. carpocapsae being more efficient than H. bacteriophora with LC50s of 34.39 and 336.63 IJs/experimental unit for S. carpocapsae and H. bacteriophora, respectively. When nematodes were applied at a concentration of 50 IJs/cm2 under semi-field conditions to the pupae, they eliminated over 25% of the larvae but no significant difference was observed between EPNs performance. Under field conditions, both species caused significant mortality when sprayed with a concentration of 25 IJs/cm2 on soil and tangerine fruits infested with fruit fly larvae with approximately 25% and 33% mortality for S. carpocapsae and H. bacteriophora, respectively. It was noted that larval mortality was higher in loam soil for H. bacteriophora and clay loam soil for S. carpocapsae as compared to sandy loam. S. carpocapsae and H. bacteriophora exhibited better-controlling potential at 25°C and 19°C than at 30°C, respectively. These findings suggest that these nematodes were highly effective at infecting fruit flies in the soil, and the superior performance of this EPN under certain soil conditions may be attributed to the higher potential of S. carpocapsae. According to this study, S. carpocapsae could potentially be implemented as a biological agent in a C. capitata management program.

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