STUDIES ON THE EPIDEMIOLOGY AND CONTROL OF MANGO ANTHRACNOSE ON THE VARIETY 'CARABAO' IN THE PHILIPPINES

Abstract

A field trial was conducted in the Cavite region of Luzon Province, the Philippines, from October 1988 to March 1989 with 40–50 year-old trees of the mango variety Carabao to study the epidemiology of anthracnose disease of mango caused by Colletotrichum gloeosporioides. The effects of pre-harvest applications of benomyl, chlorothalonil and prochloraz, each at 250ppm, on post-harvest development of anthracnose was also assessed. Five pre-harvest applications of benomyl, from flowering to fruit set, and one application a month later gave excellent control of post-harvest development of anthracnose on fruit harvested 112 days after floral induction and incubated at ambient temperatures for 16 days. Chlorothalonil and prochloraz were intermediate in effectiveness between benomyl and the control where no fungicide was applied. Data from spore-trapping showed that benomyl applications had significantly reduced the number of conidia disseminated by rainfall compared with those recovered from control trees, one week before harvest. Dipping mangoes from all four treatments in hot benomyl (850ppm at 52–54°C for 10 minutes) on the same day as harvest gave 100% control of the disease post-harvest. A technique devised to assess the development of quiescent infections on mango fruit during maturation detected few colonies of C. gloeosporioides in any of the treatments. This indicates that either the technique is insensitive to quiescent infections of this pathogen/host combination or that few quiescent infections occurred during this drier than average season. Preliminary work with a polyclonal antibody raised against an isolate of Colletotrichum gloeosporioides, was successful in labelling conidia of C. gloeosporioides from the Philippines and other countries using an immunofluorescence marker.