Current status on occurrence and management of major diseases of mango in Taiwan.
Ann P. J., Tsai J. N., Ni H. F., Yang H. R.
Author Affiliation: Taiwan Agricultural Research Institute, Council of Agricultural (COA), Wufong, Taichung, Taiwan.
Plant Pathology Bulletin 22 : 67-92
Abstract : In Taiwan, the major infectious diseases of mango (Mangifera indica) are blossom powdery mildew, anthracnose, stem end rot and fruit rot, sooty mould, bacterial black spot and algae spot. Among them, anthracnose, stem end rot and fruit rot caused by fungal pathogens, and black spot caused by bacterial pathogen are the most important diseases, causing severe economic losses. For example, anthracnose of mango was considered one of the major limiting factors affecting domestic and export markets of mango fruits. Powdery mildew of mango occurs in the spring from February to April annually. The pathogen mainly damages spikes, young fruits and young leaves, causing premature fallen of flowers, young fruits and leaves. Pesticides applied at the right time can effectively control the disease. Mango anthracnose occurs year-round in Taiwan. The fungi, Colletotrichum gloeosporioides and P. acutatum, usually attack flowers, fruits, young shoots, immature leaves and other wounded tissues, and cause blight, necrosis, spots as well as fallen of infected tissues prematurely. Also, the anthracnose pathogens are capable of establishing as latent infection in growing leaves and fruits and the disease symptoms are visible only when the infected fruits and leaves are matured. Most of the commercial mango varieties in Taiwan, including the most popular variety Irwin', are susceptible to anthracnose. High humidity from frequent rainfall is the most important factor favorable for the development of anthracnose disease. Integrated disease management (IDM) is recommend as an important strategy for control of anthracnose and the methods for IDM include field sanitation, pruning and removal of diseased twigs and leaves, scheduled chemical sprays, bagging at early fruit formation stage, application of antagonistic microorganisms and covering orchard ground with vinyl sheets. Stem end rot and fruit rot caused by Botryosphaeriaceae are the major postharvest diseases of mango fruits. Infected fruits develop symptoms of soft rot rapidly during storage period. Methods to control stem end rot and fruit rot of mango include early fruit bagging and chemical control in the field, adequate fruit picking skill to avoid injury of fruit tissues and avoid harvesting fruits in rainy days. Bacterial black spot of mango, caused by Xanthomonas campestris pv. mangiferaeindicae, occurs on fruits and other wounded tissues, including leaves, stems and trunks in the orchard. The disease is most serious in regions with gusty wind or during typhoon season, which often causes severe damages to mango fruits, leaves and branches. The late-maturing varieties 'Keitt' mango and many native mango varieties are highly susceptible to bacterial black spot. The methods for managing this disease include field sanitation, removal of susceptible varieties in a mixed plantation, planting resistant varieties, establishing windbreaks for orchards in windy-areas, early fruit bagging, and chemical control using copper compounds. Sooty mould caused by Ascomycetes and black mildew caused by Meliola mangiferae occur generally in poorly managed orchards. These diseases are managed by field sanitation and control of honeydew-secreting insects. Phytophthora fruit rot caused by Phytophthora palmivora occurs occasionally in the rainfall season and the disease can be managed by the fruit bagging method to avoid infestation of mango fruits by the pathogen. Algal leaf spot occurs under humid weather and the disease can be prevented by application of copper compounds.