Powdery mildew is a very serious disease of mango, affecting almost all cultivars in all mango-growing regions of the world. It is caused by the fungus Oidium mangiferae and causes extremely high reductions in yield.
The fungus attacks inflorescences, leaves, and young fruits.
The characteristic symptom of the disease is the whitish, superficial, powdery fungal growth, mainly on inflorescences. Affected flowers do not open and in most cases, they shed prematurely. Young fruits may also be covered with powdery growth and drop off prematurely. Poor fruit set and heavy flower and fruit drop result in severe yield losses, sometimes reaching as high as 70–90% on an individual plant.
Oidium mangiferae survives from one season to the next as mycelium in dormant buds and as haustoria on old infected leaves.
After landing on the plant tissue, a conidium of O. mangiferae germinates, enters a stoma/pore and then grows. After two or three weeks, the fruiting bodies grow out of the stomata and release conidia into the air, to be carried to other plants or plant parts.
It usually takes about 7-10days from the time of infection to development of symptoms.
The disease is spread by wind-borne conidia from other mango trees or from within an infected tree’s canopy.
Initial infection with O. mangiferae is promoted by warm temperatures and moderate relative humidity, although development of the disease is favoured by cool, dry conditions.
The fungus survives under dense foliage during off-season.
Signs & Symptoms
Oidium mangiferae attacks the young tissue of all parts of the inflorescence, leaves and fruits. Infection shows initially as small patches of white powdery mycelium, which may later coalesce to cover large areas. On older leaves and fruits, infected tissue has a purplish-brown cast as the white growth weathers away.
Leaves; young infected leaves may become distorted. Grey necrotic lesions appear on the upper side of the leaf, and leaves tend to curl downwards. In severe cases, they become brown and dry, and drop from the plant.
Inflorescences; flowers are most susceptible to infection once they have begun to open on the panicles, about 3-5 weeks after bud break. Flowers and stalks can become severely infected and sepals are more susceptible than petals. Infected flowers may fail to open and may drop from the panicle. Oftenly inflorescences become completely covered by the mildew and eventually blacken or become brown and dry. Severe blossom infection can result in complete loss of fruit.
Fruits; as infected newly set fruit develop, the epidermis of the infected area cracks and corky tissue is formed. The entire fruit may become covered by the mildew and may become yellow and misshapen.
Although powdery mildew is a very serious disease of mango, control measures are available. The following methods are employed in the control and/or management of powdery mildew of mango;
Chemical Control Methods
This is the best and more effective management strategy for controlling the disease. The following fungicides are recommended for use in prevention and eradication of powdery mildew disease of mango;
- ABSOLUTE 375SC 10ml/20l
- JUPITER 125SC 15ml/20l
- CHARIOT 500SC 20ml/20l
- EXEMPO CURVE 250SC 15ml/20l
- RANSOM 600WP 15g/20l
- EXPLORER 3 SL 10ml/20l
- MEGAPRODE LOCK 525WP 30g/20l
- MILESTONE 250SC 10ml/20l
- TOMAHAWK 250EC 10ml/20l
Non-chemical control methods
The following practices help in reducing the fungus inoculum, prevent the spread of the disease and provide a condition that does not favour the development of the disease.
- Regular pruning of infected inflorescences at an early stage.
- Removal of fallen leaves, inflorescences, and malformed fruits from the tree base
- Use of tolerant/resistant varieties
- Proper weed control
- Minimizing field movements from infected areas to non-infected zones
- Ensuring proper spacing of the trees
- Whenever spraying, it is advisable to mix the fungicide with INTEGRA 3ml/20l, which improves the efficacy of the fungicide by acting as a sticker, spreader, and penetrant.
- Timely control of the disease helps reduce/prevent losses attributed to its infection.
- Alternating different fungicides throughout a plant’s season prevents the fungus from developing resistance over any of the fungicides.
- Fungicides should be reapplied after 1-2weeks.
- A proper nutrition builds/boosts the plants’ immunity against infections.