Mango Anthracnose is a fungal infection caused by the fungus Colletotrichum gloeosporioides and is presently recognized as the most destructive field and post-harvest disease of mango worldwide.
It is the major disease limiting fruit production in all countries where mangoes are grown, especially where high humidity prevails during the cropping season.
The post-harvest phase is the MOST damaging and economically significant phase of the disease, which directly affects the marketable fruit rendering it worthless. This phase is directly linked to the field phase where initial infection usually starts on young twigs and leaves and spreads to the flowers, causing blossom blight and destroying the inflorescences and even preventing fruit set.
Mango Anthracnose Cycle
Conidia/spores are the most important type of inoculum in mango orchards. They are produced on lesions on leaves, twigs, panicles and mummified fruits. The conidia can be rain-splashed to other leaves or flowers to cause secondary infections, thus making the disease polycyclic in these organs.
Developing fruits can be infected and some aggressive isolates can cause pre-harvest fruit losses.
In the case of postharvest mango anthracnose, developing fruit are infected in the field, but infections remain quiescent until the onset of ripening, which occurs after harvest. Once the climacteric period of the fruit starts, lesions begin to develop. There is usually no fruit-to-fruit infection, hence postharvest anthracnose is considered a monocyclic disease.
Mango fruit can also be infected with conidia from isolates of Colletotrichum sp. from other host plants like as avocado, papaya and citrus.
Wet, humid, warm weather conditions favor mango anthracnose infections in the field.
Mango Anthracnose Signs and Symptoms
The anthracnose fungus invades inflorescences, fruits, leaves and stems of mango plant.
Leaf anthracnose appears as irregular-shaped black necrotic spots on both surfaces of the mango leaf. Lesions usually coalesce forming large necrotic areas, oftenly along the leaf margins. Severely infected leaves curl. Lesions develop primarily on young tissue and conidia are formed and can be observed in lesions of all ages. In older leaves, lesions do not develop, but latent infections are formed and the fungus remains dormant until the tissue senesces. Growth then resumes and fruiting structures are produced in the necrotic tissue. Under favorable conditions, spores are dispersed and invade young twigs causing twig dieback in some cases
Panicle anthracnose or blossom blight affects both the inflorescence stalk and the individual flowers. Infection reduces fruit set and production considerably, since attacked flowers are killed. In the stalk, elongated dark gray to black lesions appear. Blighted flowers are dry and their color varies from brown to black.
Small emerging fruits can be infected and aborted. Larger fruits aborted because of other physiological causes are usually mummified and the mummies are invaded saprophytically by the fungus on which they sporulate profusely.
Postharvest anthracnose appears as rounded brown to black lesions with an indefinite border on the fruit surface. Infection in larger fruits does not usually develop into lesions. After initial establishment in the fruit, the fungus remains latent or dormant until the fruit begins to ripen. Dark depressed circular lesions develop on the ripening fruit and increase rapidly in size.
Lesions of different sizes can coalesce and cover extensive areas of the fruit, typically in a tear-stain pattern, developing from the basal toward the distal end of the fruit. These lesions are usually restricted to the peel, but in severe cases the fungus can penetrate even the fruit pulp. In advanced stages of infection, the fungus produces acervuli and abundant orange to salmon pink masses of conidia appear on the lesions.
Mango Anthracnose Management
The following premium fungicides are recommended for prevention and eradication of mango anthracnose.
- Prune trees yearly and remove fallen plant debris from the ground.
- Use resistant plant varieties
- Wider plant spacing inhibits severe epidemics.
- Intercropping with other types of trees that are not hosts of mango anthracnose inhibits epidemics.
- If this fungal problem is common, DO NOT save your own seed from plantings.
- To avoid spreading the disease, keep out of gardens when plants are wet and make sure to disinfect all garden tools after use.
- Do not compost infected leaves, fruit or stems and thoroughly clean up garden areas in the fall, after harvest, to reduce over wintering sites for the fungal spores.
- Seed treatment with BIODISTINCTION XTRA helps to control seed coat infections.
- Fungicides should be mixed with INTEGRA 3ml/20l, which improves the efficacy of the fungicide by acting as a sticker, spreader, wetter and penetrant.
- Alternating different fungicides throughout a plant’s season prevents the fungus from developing resistance over any of the fungicides.
- Timely control of the diseases is very critical.