Powdery Mildew: A Devastating Disease of Mango Trees
Powdery mildew is a highly destructive disease that affects mango trees worldwide, impacting various cultivars in different regions. The disease is caused by the fungus Oidium mangiferae and can result in significant reductions in crop yield.
Symptoms of Powdery Mildew
The disease primarily attacks inflorescences, leaves, and young fruits. One of the key symptoms is the appearance of whitish, powdery fungal growth on the inflorescences. Affected flowers fail to open and often fall prematurely. Additionally, young fruits may also display a powdery coating and drop off before reaching maturity.
These issues lead to poor fruit set and heavy flower and fruit loss, resulting in substantial yield losses, sometimes ranging from 70% to 90% per affected plant.
Oidium mangiferae survives from one season to the next by existing as mycelium in dormant buds and as haustoria on infected leaves. When the fungus lands on plant tissue, it germinates from a conidium, enters a stoma or pore, and begins to grow. After approximately two to three weeks, fruiting bodies emerge from the stomata, releasing conidia into the air.
These conidia are then carried by wind to infect other plants or different parts of the same plant. The development of symptoms typically occurs around 7-10 days after infection. The disease spreads through wind-borne conidia from other mango trees or within the canopy of an infected tree. While initial infection thrives in warm temperatures and moderate humidity, the disease’s progression is favored by cool and dry conditions. The fungus can survive during the off-season under dense foliage.
Signs and Symptoms
Oidium mangiferae affects young tissues in all parts of the inflorescence, leaves, and fruits. Initially, small patches of white powdery mycelium appear, which may eventually merge to cover larger areas. As the white growth weathers away, infected older leaves and fruits may develop a purplish-brown coloration. Infected leaves may become distorted, with gray necrotic lesions forming on the upper side and a tendency to curl downwards. In severe cases, leaves turn brown, dry up, and fall from the tree.
Infected flowers on the inflorescences are highly susceptible, particularly after they start to open, around 3-5 weeks after bud break. Sepals are more vulnerable than petals, and infected flowers often fail to open or drop prematurely from the panicle. Inflorescences can become entirely covered with mildew, eventually turning black or becoming brown and dry.
Severe blossom infection can lead to the complete loss of fruit. Infected young fruits exhibit cracked epidermis and the formation of corky tissue. The entire fruit may become covered in mildew, resulting in a yellow, misshapen appearance.
Management of Powdery Mildew
While powdery mildew poses a significant threat to mango trees, effective control measures are available. The following management strategies can be employed:
1. Chemical Control Methods
Chemical control is considered the best and most effective approach to managing the disease. The use of recommended fungicides, such as ABSOLUTE 375SC, JUPITER 125SC, and CHARIOT 500SC, helps prevent and eradicate powdery mildew. It is crucial to follow the specified dosages and application guidelines for each fungicide.
2. Non-chemical Control Methods
Implementing non-chemical practices can help reduce the fungal inoculum, limit the disease’s spread, and create unfavorable conditions for its development. These methods include:
- Regular pruning of infected inflorescences at an early stage.
- Removing fallen leaves, inflorescences, and malformed fruits from the base of the tree.
- Planting tolerant or resistant mango varieties.
- Maintaining proper weed control.
- Minimizing movement between infected and non-infected areas.
- Ensuring adequate spacing between trees.
When applying fungicides, it is advisable to mix them with INTEGRA, as it acts as a sticker, spreader, and penetrant, improving the efficacy of the fungicide. Timely disease control can help minimize losses caused by infection. To prevent the development of resistance, it is recommended to alternate between different fungicides throughout the plant’s growing season.
Fungicides should be reapplied every 1-2 weeks for optimal effectiveness. Providing proper nutrition to the plants enhances their immunity against infections.
Powdery mildew is a severe disease that affects mango trees worldwide, causing significant reductions in yield. By employing chemical and non-chemical control methods and adhering to proper practices, farmers can effectively manage and mitigate the impact of powdery mildew on their mango crops. Timely intervention and careful disease management contribute to healthier mango trees and improved fruit production.