The Greater melon fly, Dacus frontalis Becker, is one of the most economically damaging pests of cucurbit fruits in Africa. The fly is considered to have a negative impact on food security in the continent. In Libya, a range of major cucurbit crops are attacked, causing extensive yield losses of up to 100%. Direct damage is caused by the larval stage, which decreases quality and quantity of the fruit production, raising concern among growers. Currently, Libyan farmers still rely mainly on extensive application of several insecticides; however, such applications often fail to suppress the fly damage. Information on other management options for the fly is limited. The aim of this chapter is to evaluate entomopathogenic fungi for use against D. frontalis and 252develop better strategies in using these biological agents for integrated fly management. The pathogenicity of five commercial biopesticides based on several strains of entomopathogenic fungi, Metarhizium anisopliae, Beauveria bassiana, and Isaria fumosoroseus, against larvae, pupae, and adult stages of D. frontalis was evaluated by using various inoculation methods under laboratory conditions. The most effective formulation, Met52 Granular biopesticide, based on M. anisopliae var anisopliae strain F52 (MET52), was selected for further investigations. A dose-response of the target pest to MET52 was examined. Effects of formulation and application time on the efficacy of the fungus were also evaluated. The results revealed that D. frontalis adults are more susceptible to the fungal pathogens than pupae. Met52 caused the greatest pathogenicity to the adults ranging from approximately 88% to 100% mortality. Pupal age and increasing rate of MET52 had no effect on pupal mortality. However, MET52 increased mortality of emerging adults by 15% when applied on young pupae. Approximately 10 days were required to get 90% adult mortality when pupae were placed into soil treated with the lowest rate tested. Also, early application of MET52 in granule form caused a significant reduction in adult emergence compared to a drench and untreated control. The effect of MET52 against D. frontalis was influenced by application time with the greatest pathogenicity recorded when the treatment occurred 2 weeks before larvae entered the soil, resulting in a 55% reduction in adult emergence rate. This is the first study to demonstrate the susceptibility of D. frontalis to entomopathogenic fungi, suggesting that early soil application of MET52 offers a promising biological control for D. frontalis.