Alternative hosts of Erysiphe quercicola in the Brazilian cashew ecosystem

Powdery mildew is currently the most important disease of the cashew plant across all producing regions of Brazil. A recent study reported the occurrence of Erysiphe quercicola as the causal agent of the symptoms on leaves, inflorescences, pseudofruits and kernels. Morphological evidence raised the question of whether different hosts of the fungus occur in areas near to cashew orchards. This study was developed to compare the fungi that cause powdery mildew in plants in the cashew ecosystem in order to understand the host relationships, and raising the possibility that alternative hosts are involved in the epidemics verified in the cashew tree. The work consisted of collecting samples of plants with symptoms of powdery mildew and carrying out morphological, phylogenetic and cross‐pathogenicity analysis of the fungal pathogens. The results of this characterization showed that annatto (Bixa orellana), sombrero (Clitoria fairchildiana) and mango (Mangifera indica) are possible alternative hosts of E. quercicola pathogenic to cashew and can therefore represent a source of inoculum for cashew powdery mildew. In addition, the occurrence of this pathogen in mango in Brazil was identified for the first time. Annatto (Bixa orellana), sombrero (Clitoria fairchildiana) and mango (Mangifera indica) are alternative hosts and possible inoculum sources of E. quercicola, the causative agent of powdery mildew on cashew in north‐east Brazil.