Mango tree diseases

Mango trees are susceptible to numerous health problems that can stunt their growth, reduce the harvest, or impair the quality of the mangoes. Spots on the leaves, blackening fruit, drying branches, or aborted flowering: these symptoms often have a specific cause. Let’s explore the main mango tree diseases, their warning signs, the factors that promote their development, and our practical solutions for limiting their impact.

Anthracnose

Anthracnose is one of the most common diseases of mango trees and also one of the most commercially damaging. It is caused by Colletotrichum gloeosporioides and its sexual stage, Glomerella cingulata . On the leaves, it causes small black spots, sometimes with the shedding of necrotic tissue, leaving a perforated appearance. The inflorescences may turn brown, break, or partially dry out. On the fruit, circular black spots appear, which enlarge, followed by browning of the pulp and more or less deep rot. What makes it so formidable is its ability to remain latent: a fruit that appears healthy in the orchard can turn black during ripening or cold storage. Rainy periods, excessive irrigation, poorly ventilated orchards, and insect damage create a very favorable environment for its development.

Mango powdery mildew

Powdery mildew, caused by Oidium mangiferae , primarily attacks young plant parts during flowering and fruit set. It is identified by a white, powdery coating, often visible on the undersides of leaves, on young inflorescences, and sometimes on small fruits. Flower buds turn black, dry out, and fall off easily. When the infection occurs during fruit set, young mangoes either drop or develop corky, net-like scars. This disease thrives in cool, dry, and windy conditions, provided there is sufficient humidity for spore germination. It develops most rapidly between 18 and 24°C, making it a disease closely tied to a specific climatic window.

Mango tree scab

Mango scab, caused by Elsinoe fawcettii , primarily affects young tissues, particularly in the two weeks following the emergence of new leaves. The first signs appear as small, water-soaked spots that then develop into pustules and brownish, corky lesions, sometimes surrounded by a halo. On young fruit, these lesions become cracked and rough, severely degrading the commercial appearance of the mango. Branches can also be affected. Sporulation requires saturated humidity, with development favored at temperatures between 20 and 28°C. Wind, rain, irrigation, and contaminated plant material contribute to its spread, which explains its high prevalence in damp or poorly ventilated plots.

Alternaria disease or black rot

Alternaria leaf spot, often caused by Alternaria alternata , is a fungal disease that can be confused with anthracnose, especially on fruit. On leaves, it causes numerous small, round, black spots, often 1 to 3 mm in diameter. Small lesions may appear on twigs. On fruit, the problem often becomes more pronounced after harvest, with superficial black spots around the lenticels, especially near the peduncle, sometimes progressing to internal rot. Conidia can be present year-round, but their release increases with high humidity. Prolonged wet periods, dense vegetation, and temperatures close to 25°C are favorable conditions. In some slightly drier or cooler conditions, it can even outcompete other post-harvest diseases.

Stem-end rot

Stem-end rot , often referred to by its English name , is caused by a group of fungi including Lasiodiplodia , Dothiorella , Phomopsis , and Pestalopsiopsis . The disease begins at the fruit attachment point and becomes most visible during ripening. The flesh deteriorates from the stem end, with dark, water-soaked spots that gradually spread. A key indicator for distinguishing it from anthracnose is the presence of dark streaks in the vascular tissue, whereas anthracnose more commonly presents as round spots on the skin. The infection can develop very early, as early as flowering, and then remain dormant before manifesting after harvest, particularly when the fruit is stored in warm conditions.

Pink disease

Pink disease caused by Erythricium salmonicolor , is most commonly seen on branches and sometimes on the trunk. It forms characteristic pinkish deposits on the bark surface, which then develop into scabs that can progress into cracks. As the infection progresses, branches die back and the tree’s vigor declines. This disease is typical of warm, humid climates, with a higher incidence in dense canopies where air circulation is poor. Unlike diseases that first appear on fruit or flowers, this one is noticed by its appearance on the wood, making it relatively easy to spot in the orchard by carefully observing the tree’s structure.

Red rust

Red rust is not caused by a fungus, but by a parasitic alga, Cephaleuros virescens . It causes rounded, orange to coppery spots on the leaves, sometimes large, with irregular borders and a shallow appearance. Its effect on the overall vigor of the mango tree is often limited, but the affected leaves quickly become very recognizable. This disease develops mainly in hot, humid climates, when the canopy remains wet for extended periods. It spreads through wind and splashing. In practice, it is primarily a visual problem and often serves as an indicator of a humid environment in which other diseases can also thrive.

Sooty mold

Sooty mold is a superficial black deposit caused by opportunistic fungi that thrive on the honeydew left by sap-sucking insects, such as scale insects or aphids. On leaves and sometimes on fruit, a black, unsightly film appears, which can cover large areas. The deposit does not penetrate deeply into the tissues, but it reduces the amount of light reaching the foliage and hinders photosynthesis.

Mango tree malformation

Mango malformation, primarily associated with Fusarium mangiferae , is among the most visually striking diseases. Young shoots become highly branched, shortened, and appear stunted and compact. Inflorescences are thickened, abnormally divided, and bear a large number of sterile flowers, often more numerous and larger than normal. The result is very poor fruit set, sometimes almost absent on affected panicles. While the disease often spreads slowly within an orchard, crop losses can be very significant on affected trees. The presence of the Aceria mangiferae mite is frequently cited in connection with this disease, adding a complex dimension to its presentation.

Bacteriosis or bacterial black spot

Mango bacterial blight, caused by Xanthomonas citri pv. mangiferaeindicae , is among the most damaging diseases when conditions are favorable. On leaves and young stems, it produces small, angular, black spots, often slightly raised and surrounded by a yellow halo. On veins and twigs, the lesions can become deeper, with gummy cankers and apical necrosis. On fruit, the signs are very distinctive: gummy black spots, streaks, and cracks in the skin, sometimes accompanied by an oozing that resembles latex tears. Heat, high humidity, windy rain, spraying, and injuries from storms or handling significantly favor this bacterium. In severe cases, losses can be very high, rendering a large proportion of the fruit unmarketable.

Sudden decline in Ceratocystis

Sudden decline caused by Ceratocystis manginecans is a highly aggressive vascular disease. It is often associated with the presence of the bark beetle Hypocryphalus mangiferae , which burrows galleries and contributes to the spread of the fungus. The crown withers rapidly, branches die back, the inner wood develops black streaks, and the trunk may show gummy oozes and insect holes. The progression can be rapid, leading to the death of the tree. This disease is striking in its sudden onset: while other diseases initially reduce fruit quality or vigor, this one directly threatens the survival of the mango tree. Its presence in an orchard should always be a cause for serious concern due to its high destructive potential.

Mango viruses: mosaic and leafroll

Viruses recently reported in mango trees, such as Mangifera virus 1 and Mangifera indica latent virus , are associated with mosaic symptoms, upward curling, and wavy edges on young leaves. Data on their actual impact in orchards remains limited, making it difficult to define their role in relation to better-known diseases. The observed signs can be mistaken for other disorders, particularly nutritional or physiological ones, which complicates understanding the problem without appropriate analysis. Based on current data, these viruses should primarily be viewed as emerging agents that expand the list of possible causes of deformed or mottled foliage.

Mango begomovirus

The Tomato leaf curl New Delhi virus , or ToLCNDV, has also been reported on mango trees. This begomovirus, transmitted by the whitefly Bemisia tabaci , typically causes leaf curl and mosaic symptoms. At this stage, its precise impact on mango cultivation is not yet well established, but its presence warrants attention, especially in areas where this virus is already circulating on other crops. It serves as a reminder that a mango tree exhibiting deformed leaves does not always fall under the usual categories of fungal or bacterial diseases alone.

Mango root nematode

The nematode Hemicriconemoides mangiferae attacks the root system and therefore acts primarily underground, with progressive repercussions throughout the above-ground portion of the tree. Roots become stunted, secondary roots become less numerous, and the tree then shows general signs of weakness: chlorosis, small leaves, leaf drop, dieback of branch tips, and reduced yield. Older trees seem to be more affected in orchards where the soil is already infested. This type of infestation can easily be underestimated because the above-ground symptoms resemble other problems of root fatigue or water stress, whereas the true origin lies within the roots.

Phytophthora rots

Rot caused by Phytophthora palmivora occurs primarily when the soil remains poorly drained and wet for extended periods. The roots turn brown and rot, the tree withers, the collar or trunk may develop cankers with gummy exudates, and the foliage shows water spots or discoloration. The fruit is not spared: circular, water-filled lesions may form, sometimes accompanied by visible mycelium when humidity is high, before premature fruit drop or mummification. This disease clearly links the health of the root system, the condition of the trunk, and the quality of the fruit. On mango trees, it often becomes widespread in areas where water stagnates or drains poorly after heavy rains.

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