Mango Anthracnose, caused by the fungus Colletotrichum gloeosporioides, is currently recognized as the most devastating disease affecting mangoes worldwide. It poses a significant threat to fruit production in all mango-growing countries, particularly those with high humidity during the growing season.
The post-harvest stage is particularly detrimental and economically significant, as it directly impacts the quality of the fruit, rendering it unsellable. This phase is closely linked to the field stage, where the initial infection typically occurs on young twigs and leaves. From there, it spreads to the flowers, causing blossom blight, destroying inflorescences, and even preventing the development of fruit.
Mango Anthracnose Cycle
In mango orchards, the most crucial type of inoculum is the conidia/spores, which are formed on lesions found on leaves, twigs, panicles, and dried-up fruits. These conidia can be dispersed by rain and splash onto other leaves or flowers, leading to secondary infections. As a result, the disease exhibits a polycyclic nature in these plant parts.
Developing fruits are susceptible to infection, and certain aggressive strains can cause fruit loss before harvest.
Regarding postharvest mango anthracnose, fruit becomes infected in the field, but the infections remain dormant until the onset of ripening, which occurs after harvesting. As the fruit enters the climacteric phase, lesions begin to develop. Typically, fruit-to-fruit transmission of the disease is rare, making postharvest anthracnose classified as a monocyclic disease.
Mango fruits can also be infected with conidia from Colletotrichum sp. isolates originating from other host plants such as avocado, papaya, and citrus.
Wet, humid, and warm weather conditions create favorable circumstances for mango anthracnose infections in the field.
Mango Anthracnose Signs and Symptoms
The fungus responsible for anthracnose infiltrates various parts of the mango plant, including inflorescences, fruits, leaves, and stems.
Leaf anthracnose manifests as irregular-shaped black necrotic spots on both sides of mango leaves. These spots often merge to form larger necrotic areas, particularly along the leaf edges. Severely infected leaves may curl. The lesions primarily develop on young tissue, and conidia can be observed in lesions of all ages. On older leaves, lesions do not form, but latent infections occur, remaining dormant until the tissue senesces. When growth resumes, fruiting structures appear within the necrotic tissue. Under favorable conditions, spores disperse and invade young twigs, occasionally resulting in twig dieback.
Panicle anthracnose, also known as blossom blight, affects both the inflorescence stalk and individual flowers. Infection significantly reduces fruit set and production, as infected flowers perish. Dark gray to black elongated lesions emerge on the stalk, while blighted flowers become dry and their color varies from brown to black.
Emerging small fruits can be infected and aborted, while larger fruits that have been aborted due to other physiological causes typically turn into mummies. These mummified fruits are then saprophytically invaded by the fungus, which abundantly sporulates on them.
Postharvest anthracnose appears as rounded brown to black lesions with indistinct borders on the fruit surface. In larger fruits, these infections typically do not progress into visible lesions. Once established in the fruit, the fungus remains dormant until the fruit begins to ripen. Dark depressed circular lesions emerge on ripening fruits and rapidly expand in size.
Lesions of various sizes can merge and cover significant portions of the fruit, often following a tear-stain pattern from the base to the tip. These lesions primarily affect the peel, but in severe cases, the fungus can penetrate the fruit pulp. In advanced stages of infection, the fungus generates acervuli, and abundant orange to salmon pink masses of conidia appear on the lesions.
Mango Anthracnose Management
For the prevention and elimination of mango anthracnose, the application of the following high-quality fungicides is recommended:
- RANSOM® 600WP: Mix 15 grams of RANSOM® 600WP with 20 liters of water.
- ABSOLUTE® 325SC: Combine 10 milliliters of ABSOLUTE® 325SC with 20 liters of water.
- Regularly prune trees and remove fallen plant debris from the ground.
- Opt for resistant varieties of mango plants.
- Increase plant spacing to discourage severe outbreaks.
- Intercrop with non-host trees to inhibit the spread of anthracnose.
- If the fungal problem is prevalent, avoid saving your own seeds from infected plantings.
- To prevent disease spread, avoid working in gardens when plants are wet and disinfect all garden tools after use.
- Refrain from composting infected leaves, fruits, or stems, and thoroughly clean garden areas in the autumn, after harvest, to reduce overwintering sites for fungal spores.
- Treat seeds with BIODISTINCTION XTRA to control seed coat infections.
- Enhance the effectiveness of fungicides by mixing them with INTEGRA at a rate of 3ml/20l. INTEGRA acts as a sticker, spreader, wetter, and penetrant.
- Employ a strategy of alternating different fungicides throughout the plant’s growing season to prevent the fungus from developing resistance to any specific fungicide.
- Timely and proactive disease control measures are crucial in managing mango anthracnose effectively.