Characterization of mango malformation disease and the interaction between the pathogen Fusarium mangiferae and the mango bud mite Aceria mangiferae

Mango malformation, caused by Fusarium mangiferae, is one of the most destructive diseases of this crop. Very little is known about the disease epidemiology and the possible association between the mango bud mite Aceria mangiferae and the fungal pathogen. Research objectives were to assess primary inoculum in the orchard, study patterns of conidial dispersal, locate the infection sites and the means of reaching it, and, determine the role of the bud mite in epidemiology of disease. Malformed inflorescences were assessed in a diseased orchard and significantly more conidia/g infected panicles were found in May and June than in April during 2006 and 2007, corresponding with higher numbers of malformed inflorescences per tree and a peak in dispersal of inoculum. No windborne bud mites bearing conidia were found in mite traps. Inoculation of leaves, branches, and buds resulted in colonization only in buds, suggesting that buds are the exclusive infection sites. Following exposure of the mite to a green fluorescent protein-marked isolate, conidia were observed clinging to its body. In inoculation experiments on leaves of mango seedlings, conidia were found inside buds only when both mites and conidia were co-inoculated on the plant, demonstrating that mites vectored conidia into apical buds. Dry malformed panicles that were placed on apical buds of potted plants were found to be infective. A significantly higher disease incidence was recorded in buds inoculated with conidia in the presence of mites than with conidia alone, demonstrating the significance of the mite in the fungal infection process. This study sheds new light on the epidemiology of the disease and the role of A. mangiferae, particularly on the mode of vectoring conidia of F. mangiferae and assisting fungal penetration. We believe that these novel findings are important steps towards developing an improved strategy for management of mango malformation disease.