Twenty isolates of the fungus Metarhizium anisopliae (Metsch.) Sorkin (Ma) were evaluated to determine their virulence against last instar and adult emergence of Mexican fruit fly, Anastrepha ludens (Loew). Larvae were exposed by immersion in a conidial suspension at a concentration of 10⁸ UFC/ml under laboratory conditions. Larvae and pupae cumulative mortality rates ranged from 37.9 to 98.75%. Thirteen isolates caused mortality rates >83.7%, and their LT₅₀ values ranged from 1.8 to 6.2 d. The Ma2, Ma8, and Ma16 isolates were evaluated at seven different concentrations ranging from 10¹ to 10⁷ UFC/ml, showing LC₅₀ values from 3.7 to 4.8 × 10⁵ UFC/ml. In a field-cage experiment, 200 ml of a conidial suspension of Ma2, at a concentration of 2.5 × 10⁶ UFC/ml, was applied on 2,500 cm² soil surface (2 × 10⁵ UFC/cm²). The fungus reduced adult emergence, 22% fewer adults emerging in a sandy loam soil, and 43% fewer in loam soil, compared with the controls. M. anisopliae may offer a preferable alternative to chemicals as a biological control agent against A. ludens.