Sensitivity to MBC fungicides and prochloraz of Colletotrichum gloeosporioides species complex isolates from mango orchards in Mexico

Anthracnose, caused by Colletotrichum spp., is the most significant field and post-harvest disease of mango worldwide and is mainly controlled through the use of systemic fungicides belonging to the methyl benzimidazole carbamate (MBC) class. In Mexico, this disease in mango has been associated with at least seven cryptic species belonging to the C. gloeosporioides complex. In this study, the distribution of sensitivity to MBC (benomyl and carbendazim) and prochloraz fungicides of 101 Colletotrichum spp. isolates obtained from 101 commercial orchards in Mexico’s most important mango-producing states was determined. All Colletotrichum spp. isolates were obtained from commercial mango orchards with applications of MBC fungicides and that had not been exposed to applications of prochloraz, or any other DMI (demethylation inhibitors) class fungicide. Isolates were evaluated using an in vitro test to determine the effective fungicide concentration at which 50% of mycelial growth is inhibited (EC₅₀) for each isolate-fungicide combination. EC₅₀ values for benomyl and carbendazim ranged from 0.0967 to 0.3995 µg mL⁻¹ (median = 0.1923 µg mL⁻¹) and from 0.0880 to 0.1703 µg mL⁻¹ (median = 0.1171 µg mL⁻¹), respectively, while those for prochloraz ranged from 0.0066 to 0.0813 µg mL⁻¹ (median = 0.0253 µg mL⁻¹). Our results revealed a wide distribution in Mexico of Colletotrichum spp. isolates from mango sensitive to MBC fungicides and prochloraz. Data obtained in this study will serve as a source of comparison of the evolution of the sensitivity of Colletotrichum spp. populations obtained from mango to MBC and DMI fungicides in the future.