Biological methods of plant protection
The most usual diseases with mango trees are fungus and bacterial diseases. The first important preventative measure is make sure that the propagation segments are healthy. The scions that were raised in tree nurseries and whose origins are maybe unclear, should be carefully examined. They shall not have been treated with any synthetic or chemical agents.
Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is the most wide-spread disease among mangoes. The varieties vary in susceptibility. Colletotrichum gloeosporioides causes anthracnose on fruits, and drop of flowers on young branches. Anthracnose always appears as a result of scurvy (Elsinoe mangiferae). Fruits stricken with anthracnose can be plunged into a hot water bath (3- 5 min. at 55degC), in order to kill off the fungus. Preventative measures are nevertheless preferable, to preclude injuries and an infection with scurvy, because anthracnose can usually only take a hold on damaged fruits that are also affected by scurvy. A case of scurvy can usually be prevented by removing all dead plant material (branches, leaves and fruit). In exceptional cases, the fungus can be brought under control again with copper strays.
While anthracnose generally attacks ripe fruits (and blossoms), a bacterial infection from Erwinia sp. can also affect young fruit. The symptoms are very similar to the flecks caused to the leaves and fruit by anthracnose. The bacteria usually survive in the ground – a heavy rainfall will then splash the spores against the lower leaves and fruits. Covering the ground can therefore help to protect against this. Active life in the soil will also help to prevent an explosive growth of bacteria. Sites where it can rain inside the blossoms can also be a problem.
Young fruit and also blossoms can be damaged by powdery mildew (Oidium mangiferae). This fungus grows during warm weather with high humidity. It attacks flowers and young fruits. A case of powdery mildew can dramatically affect the harvest. An open, well-ventilated orchard can prevent mildew. In acute cases, mildew can also be brought under control with sulphur. When carrying this out, there should be no wind blowing, and the leaves should still be moist with dew.
The leaf spot disease (Cercospora mangiferae) on mangoes is visible as dented spots on leaves and fruit. The same applies for this fungus, an open and quick-drying tree population is the best protection against infection. Fruit infected with Cercospora can no longer be sold, furthermore, both the leaf spot disease and scurvy prepare the way for anthracnose. In exceptional cases, the leaf spot disease can be brought under control copper sprays.