THE EFFECT OF CLIMATIC FACTORS ON COLLETOTRICHUM-GLOEOSPORIOIDES, CAUSAL AGENT OF MANGO ANTHRACNOSE, IN THE PHILIPPINES

The epidemiology of the anthracnose pathogen of mango, Colletotrichum gloeosporioides, was studied over two growing seasons in the Philippines. This pathogen spreads within tree canopies as water-borne conidia during rainfall, and causes symptoms on young flush leaves, flowers and fruit. Infection studies with leaves and fruit incubated at different temperatures and humidities led to the derivation of a logistic regression model of the percentage of conidia forming appressoria. This model was compared with a similarly derived model from work in Australia; it appeared that the Philippine isolates of C. gloeosporioides were adapted to the higher mean temperatures of the Philippines. Conidia were observed to germinate and form appressoria at relative humidities (RH) between 95 and 100%, even though free surface moisture was only visible at 100% RH. This model was used retrospectively to estimate infection levels in two field trials which had been established to compare pre- and post-harvest practices in the control of the disease. Using this information to plan applications of a curative fungicide might have resulted in four fewer sprays in the first trial and one less in the second, compared with the standard protective spray programme employed.