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Background Studying the ecology of biocontrol-agents is a prerequisite to effectively control medfly (Ceratitis capitata (Diptera: Tephritidae)) with entomopathogenic fungi. In this context, factors affecting the occurrence and distribution of medfly-associated entomopathogenic-fungi were studied. Soil samples (22) were collected from natural and cultivated areas of Souss-region Morocco. Results A total of 260 fungal isolates belonging to 22 species and 10 genera were obtained by using medfly pupae as bait. Medfly-associated fungi were detected in all studied soils and pupae infection percentages ranged from 3.33% to 48%. Two genera, Fusarium and Beauveria were the most frequent with 83 isolates (32%) and 50 isolates (19.23%) respectively. Pathogenicity test of isolated species against medfly pupae showed high mortality rates up to 91% for some strains. Principal component analysis (PCA) demonstrated a strong influence of origin, physical, and chemical properties of soil on the abundance of these fungi. In general, medfly-associated fungi were more abundant in soils with moderate pH (7.5 to 8) having high sand and organic content. High relative humidity negatively influenced the abundance of these fungi. Both factors directly affected the fungal infection percentages in pupae. The response of fungi to these parameters varied among species. According to principal component analysis (PCA), the soils of argan fields and forests were more suitable for the development of medfly-associated fungi than citrus orchards. Conclusions These results guide identifying suitable soils for the effective application of entomopathogenic fungi as biological control agents. In summary, isolated indigenous strains seem to be a promising option to control C. capitata.

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Abstract:The present study forms a part of biological control against the medfly (Ceratitis capitata) and seeks to isolate and determine the diversity of the medfly-associated entomopathogenic fungi in soil samples collected from Argane (Argania spinosa) forest, in different localities of Souss-Massa region. Search and isolation of the indigenous populations of Ceratitis capitata entomopathogenic fungi was carried out by using larvae of this pest as baits. After trapping, isolation and identification of fungal isolates, a pathogenicity test was used to select fungal strains that have significant virulence potential against the Mediterranean fruit fly. The degree of virulence was estimated by the ability of the fungus to induce the disease and/or the death in the insect and also by calculating the lethal time 50 (LT50). The obtained results were clearly demonstrated the sensitivity of medfly to tested fungal strains and particularly to strains of Fusarium sp., Aspergillus niger and Scopulariopsis sp. that have shown high mortality rates (more than 84%) and to Trichoderma harzianum, Scedosporium sp., Epicoccum sp. and Ulocladium sp. with more than 70% mortality for the two tested concentrations. Furthermore these strains showed short LT 50 (less than 83 hours). All these results confirm the presence of entomopathogenic fungi of Ceratitis capitata in Argane soil, and prove the potential of entomopathogenic fungi for biocontrol of the Mediterranean fruit fly under laboratory conditions.