Black Fungus on Mango Tree: 8 Possible Mango Tree Diseases

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The dark substance found on Mango trees is frequently caused by sooty mold, a type of fungal infection. However, there could be other reasons for this issue, including anthracnose, mango sooty blotch, black spot, or bacterial canker. Conducting a thorough examination of the tree for any additional symptoms will aid in determining the root cause.

You don’t need to become an arborist to correctly identify what’s going on with your mango tree.

Carefully read through the possible causes and the tips for prevention and treatment of disease below to diagnose and eliminate that strange black fungus on your mango tree.

Black Fungus on Mango Tree – Possible Causes

Among the myriad issues that afflict mango trees, some of the most common include sooty mold, anthracnose, and mango sooty blotch.

Let’s explore the details of these and other fungal threats.

1. Sooty Mold

Often appearing as a velvety black substance on the surface of mango leaves and other parts of the mango tree, sooty mold is less of a direct harm and more of an indicator of an underlying pest problem.

This fungal disease takes root on honeydew, a sugary substance excreted by pests such as aphids and whiteflies.

While the sooty mold itself doesn’t feed on the mango tree, its presence can reduce the tree’s photosynthesis capabilities by blocking sunlight.

Over time, if left unchecked, it can lead to weakened trees and reduced mango fruit yields.

The first signs of this fungal disease are the appearance of black spots and a sooty coating on the mango leaves and other susceptible parts of the tree.

While treating the sooty mold by wiping off the black substance or using a mild soapy solution is possible, the crucial step lies in managing the pests producing honeydew.

This involves using natural predators like ladybugs or applying appropriate insecticides.

Additionally, ensuring proper air circulation by pruning dense foliage can help reduce the conditions favorable for mold growth.

2. Anthracnose

Anthracnose is one of the most common mango tree diseases, especially in regions with warm temperatures and high humidity.

Caused by the fungus Colletotrichum gloeosporioides, it’s particularly destructive during the rainy season.

Symptoms of this fungal disease often appear as dark, sunken spots that turn rust-red on leaves, stems, flowers, and fruits. Over time, these spots may enlarge and cause a dieback of twigs.

On mango fruit, the disease symptoms present as circular, sunken black spots. The damage to young fruit is particularly severe, leading to fruit lesions that will be covered with corky tissue, fruit staining, or even fruit drop.

For effective management, growers often rely on copper fungicides (found here) to combat this fungal disease.

Additionally, selecting anthracnose-resistant cultivars of mango can be a preventive measure.

Maintaining a consistent and timely program of fungicidal sprays, especially during rainy conditions, is essential.

Ensure the tree is thoroughly coated with the fungicide to prevent the disease’s spread to new growth.

3. Mango Sooty Blotch

While sooty blotch and anthracnose may seem similar in appearance, mango sooty blotch is a distinct disease. This fungal disease presents itself as irregular black spots on the mango fruit’s surface.

Unlike anthracnose, these spots remain superficial and don’t cause deep lesions. The primary concern with mango sooty blotch is the fruit’s aesthetic appeal, which can affect market value.

Trees that grow in regions with warm, humid climates are particularly susceptible to this disease as the disease is fostered by rainy conditions.

While the fungus doesn’t severely harm the tree or the mango fruit’s edibility, it’s crucial to manage it to ensure marketable produce.

Prevention strategies include ensuring the tree has good air circulation, pruning where necessary, and keeping the foliage dry.

Additionally, fungicides used to treat anthracnose often prove effective against sooty blotch, especially when applied in the early spring and again 10 to 21 days later to protect the blossoms.

4. Black Spot

Black spot is a fungal disease that can plague mango trees, manifesting as small, dark black spots on the mango leaves, blossoms, and sometimes on young fruit.

Over time, these spots might expand and cause the leaves to turn brown and drop prematurely. This can lead to reduced photosynthesis and a weakened tree overall.

The disease symptoms appear especially in fruit trees that thrive in regions with high humidity and warm temperatures as these conditions are conducive to its development.

For treating black spot, it’s advisable to begin with good cultural practices.

Removing and destroying infected leaves, especially those that have fallen to the ground, can prevent the fungus from overwintering and returning the following season.

Applying fungicides, especially copper fungicides, can be effective if done early in the season and regularly thereafter.

As with many fungal diseases, ensuring that the tree is thoroughly coated with the fungicide can hinder the disease’s progress.

5. Tar Spot

The name itself is descriptive of this disease. Tar spot appears on the mango leaves as raised black spots that resemble droplets of tar.

Rarely afflicting mango trees to a severe degree, it’s more of an aesthetic issue than a significant health concern for the mango tree.

The fungal diseases attack emerging leaves, but as the leaves mature, the development of the fungus slows down.

For management, regular inspections and promptly removing infected leaves can curb its spread.

Since it’s not a highly aggressive disease, maintaining the overall health of the mango tree and ensuring optimal growing conditions are usually sufficient.

However, if the infestation becomes severe, fungicides can be applied, targeting the early stages of leaf development.

6. Mango Scab

Mango scab, caused by the fungus Elsinoë mangiferae, is another fungal disease that attacks mango trees. The disease symptoms present as circular, raised scabby spots on leaves, twigs, and fruit.

These scabs can cause deformation in young fruit and are often accompanied by a velvety appearance.

While mango scab doesn’t generally result in significant crop loss, it affects the aesthetic appeal of the fruit, making it less marketable.

For treatment, copper-based fungicides have proven effective. It’s crucial to apply the fungicide in the early stages of the mango tree’s development, ensuring the young fruit and foliage are well protected.

Note that an anthracnose spray program also controls scab.

7. Advanced Powdery Mildew

Powdery mildew is another fungus that afflicts mango trees. This disease is easily recognizable by the white, powdery substance that appears on the mango leaves, blossoms, and occasionally, young fruit.

If left untreated, powdery mildew can cause blossom blight, resulting in a lack of fruit set and defoliation of the tree. As the disease progresses, the mango leaves begin to turn brown or black and eventually fall off.

To manage this fungal disease, pruning for better air circulation can help reduce the tree’s susceptibility.

Fungicides, especially those with sulfur or neem oil, can be effective when applied at the first sign of the disease.

Regular inspections and treatments, ensuring that the entire tree is thoroughly coated, can keep this disease at bay.

8. Bacterial Canker

Caused by the bacteria Xanthomonas campestris, bacterial canker is a severe disease that can affect multiple parts of the mango tree.

Symptoms include water-soaked lesions on leaves, which later turn brown, as well as cankers on stems and twigs. These cankers can lead to bark cankers, gumming, and dieback of branches.

The disease is most damaging to young trees and may even kill them if not treated promptly.

To manage bacterial canker, pruning off infected areas is crucial. It’s vital to disinfect pruning tools between cuts to prevent spreading the bacteria.

Copper-based sprays can provide some control, but the key is early detection and intervention.

Conditions That Favor Disease Development

Mango trees, like many fruit trees, thrive in regions with warm temperatures and a good balance of sunlight and moisture.

However, these very conditions can sometimes favor the onset and spread of various diseases, especially if not managed correctly.

Humidity and Moisture

High humidity, fostered by rainy conditions and heavy dews, provides the perfect environment for fungal spores to germinate and thrive. Sooty mold and powdery mildew are particularly happy in these conditions.

When mango leaves remain wet for extended periods, the chance of fungal infection rises exponentially.

Overhead watering or frequent rains can leave mango leaves wet for prolonged periods, setting the stage for many fungal diseases.

Temperature

While mango trees flourish in warm temperatures, prolonged warmth, especially during the night, can escalate the growth rate of fungal pathogens.

Some fungal diseases use warm temperatures to their advantage, rapidly multiplying and affecting large areas of the mango tree in a short time.

Poor Air Circulation

Trees that are closely planted or not pruned regularly can suffer from a lack of air circulation. This lack of airflow can trap moisture on the leaves and branches, further promoting fungal growth.

Proper pruning ensures that every part of the mango tree receives adequate air, reducing the chance of fungal diseases taking root.

Soil Conditions

Soil health is vital for a tree’s overall well-being. Mango trees that are planted in poorly draining soils can become susceptible to root rot diseases.

Additionally, trees growing in regions with a history of specific pathogens in the soil can become victims of diseases like Verticillium wilt, where the tree’s roots and vascular system get infected.

Stress

Trees under stress, whether from pests, nutritional deficiencies, or environmental conditions, are more vulnerable to diseases.

A stressed tree has a weakened immune response, making it easier for pathogens to attack susceptible parts of the tree.

Overfertilization

While fertilizers are essential for the tree’s growth, overfertilization can lead to excessive tender growth, which is more susceptible to fungal infections.

A balanced nutrition regimen is crucial to ensure the tree remains healthy without promoting unwanted rapid growth.

Disease Prevention in Mango Trees

Maintaining the health and well-being of a mango tree means proactively preventing the onset of diseases. Here’s how one can manage mango diseases:

• When planting multiple mango trees, ensure there’s adequate spacing between each. This promotes better air circulation, reducing the chances of diseases that thrive in stagnant, humid conditions.
• Prune your mango tree annually to remove dead or diseased branches. This improves air circulation and reduces the number of potential sites for fungal spores to lodge and grow. Sanitize your pruning tools before and after use to prevent the spread of pathogens.
• Healthy, well-draining soil is crucial. Ensure the ground around your mango tree doesn’t retain excessive moisture, which can be a breeding ground for fungi.
• Regularly checking soil pH and nutrient levels can also help in keeping the tree healthy, making it less susceptible to diseases.
• Instead of overhead watering, use drip irrigation or water at the base. This prevents water from settling on mango leaves, which can foster fungal growth.
• If you’re planting a new mango tree, consider opting for disease-resistant cultivars of mango. These are genetically more resistant to certain diseases and can significantly reduce the chances of infection.
• Regularly inspect your mango tree for the first signs of any disease symptoms. Early detection is crucial for effective disease management.
• Always keep the area around the mango tree free from fallen leaves, fruit, or branches. These can be potential carriers of disease-causing pathogens.

How To Treat Mango Tree Diseases

Treating a sick mango tree effectively requires a combination of cultural, biological, and chemical approaches.

• Fungicides: Copper fungicides can be particularly useful. Ideally, the tree should be thoroughly coated with the fungicide before infection occurs. It’s best to apply fungicide in the early spring and again 10 to 21 days later to protect the panicles of blossoms.
• Natural Remedies: Some natural remedies, such as neem oil or baking soda solutions, can be effective against certain mild fungal infections. These are environmentally friendly and can be a good first step before resorting to chemical treatments.
• Improved Sanitation: Ensure the area around the tree is always clean. Removing and destroying infected parts of the mango tree can prevent the spread of the infection to new growth.
• Enhanced Nutrition: A well-fed mango tree is better equipped to resist diseases. Ensure your tree receives all the necessary nutrients, but avoid overfertilization.
• Protection from Pests: Many diseases are transmitted by pests. Using organic or chemical pest control measures can not only prevent pest damage but also reduce the risk of diseases they might bring.
• Isolation: If one tree is infected, isolate it by pruning or even removing it if necessary to protect other nearby trees.
• Consistent Monitoring: Once a disease has been identified and treated, continue monitoring the tree. Some diseases can recur, and early detection is crucial for effective management.
• Consultation: If you’re unsure about a disease or its treatment, consult your local extension office. They can provide expert advice tailored to your specific situation.

Related Questions:

How Do You Treat Black Mold on a Mango Tree?

The presence of sooty mold indicates an underlying pest problem as this fungus thrives on the honeydew excreted by pests like aphids, scale insects, and whiteflies.

Before treating sooty mold, address the pests causing the issue. Natural predators, insecticidal soaps, or specific insecticides can help reduce pest populations.

Use a soft cloth or sponge with mild soapy water to gently wipe away the mold from mango leaves and branches. Ensure you rinse the areas of the mango tree thoroughly afterward.

What Is the Best Fungicide for Mango Trees?

The best fungicide often depends on the specific disease you’re treating. However, copper fungicides are widely regarded as effective for a number of mango tree diseases.

Before applying, always identify the disease, follow label instructions, and rotate different types of fungicides to avoid resistance issues.

Closing Thoughts

While there are numerous mango tree diseases, the key to managing them successfully is correctly identifying mango disease symptoms.

Regular inspection, proper treatments, and seeking expert advice when unsure can ensure your mango tree remains healthy and productive.