Comparative epidemiology of Colletotrichum species from mango in northeastern Brazil

Anthracnose, caused by various species of Colletotrichum, is the most common disease affecting mango trees in northeastern Brazil. This disease limits production and drastically reduces fruit quality, which directly affects the export of the fruit. In this study, we investigated the virulence of five species of Colletotrichum prevalent in the orchards of Northeastern Brazil (C. asianum, C. dianesei, C. fructicola, C. karstii and C. tropicale) with respect to three mango cultivars and four alternative hosts. We also determined the influence of temperature on the severity of the disease induced by these Colletotrichum species and the effect of fungicides on the mycelial growth of the fungi. In general, the mango cultivars were susceptible to the five Colletotrichum spp., although C. karstii did not cause an infection in the Palmer and Keith cultivars. All Colletotrichum species exhibited low virulence in the Tommy Atkins cultivar. The Colletotrichum species were pathogenic on the alternative hosts (papaya, banana, guava and bell pepper). Our results suggest that these alternative hosts may serve as a potential inoculum source. For the Colletotrichum species, temperatures between 25 and 30 °C produced larger lesions; however, the different species exhibited different thermal requirements for maximum virulence in the fruits. The Colletotrichum species demonstrated reduced mycelial growth in the presence of thiophanate-methyl, difenoconazole and azoxystrobin fungicides, regardless of the active ingredient. The sensitivity response varied according to the fungicide and the species of Colletotrichum.