If you notice abnormal spots on your mango tree's flowers, you are dealing with anthracnose, a fungal infection that can lead to severe damage. Provide proper care to your mango trees, as healthy plants are less likely to experience disease problems than poorly maintained trees. Consider other symptoms on flowers as well as the rest of the tree for an accurate diagnosis before beginning treatment.
Care for your mango tree by growing it in a location that provides full sun exposure, as any amount of shade can negatively affect development of fruit and the tree itself. Cultivate your mango plant in any type of soil provided it is extremely well drained. Mango trees are sensitive to cold, so trees need an environment in which temperatures remain above 40 degrees Fahrenheit, according to the Texas AgriLife Extension Service. This tree needs extra protection in the home landscape as it is sensitive to herbicides. Isolate trees, if necessary, from other plants to avoid accidental chemical drift.
To protect mango trees from weed problems, lay a 2- to 6-inch layer of organic mulch like shredded bark on the soil surrounding your mango tree without allowing the mulch to touch its trunk, according to the University of Florida Institute of Food and Agricultural Sciences Extension. Prune your mango trees annually to remove weak twigs.
Anthracnose fungal disease is the mango's most damaging ailment, according to the University of Florida IFAS Extension. Caused by the fungal pathogen Colletotrichum gleosporioides, this disease is spread sporadically in water. Warm, humid or rainy conditions encourage disease growth. Anthracnose begins its infection with a display of near-black irregular spots on flowers and leaves that grow into larger lesions of dying plant tissue. On fruit, spots also occur, resulting in depressed areas of dying tissue. As soon as you notice symptoms, begin treatment.
As anthracnose disease spreads on mango flowers, areas of dying plant tissue increase until the flower dies. Infected mango fruits typically drop early from the tree and fruit that initially appears unaffected quickly decays upon ripening. Other plant parts like branches experience dying plant tissue and dieback. Anthracnose leads to a decrease in fruit production when flowers die or, if fruits have already developed, destruction of your crop.
Treating the entire plant as a means of keeping flowers healthy is essential for fruit production, as fruits are produced from a small number of flowers on the mango tree. Begin by choosing cultivars known for their resistance to anthracnose. For example, Zill is considered resistant, whereas Irwin is known for its susceptibility, according to the University of Hawaii at Manoa. Regularly collect and destroy fallen plant parts on which disease may live to decrease the spread of infection. Apply a fungicide to your tree for chemical control. Use a fungicide with the active ingredient chlorothalonil or use neem oil at a concentration of 70 percent, according to the University of Hawaii at Manoa.