Description of Powdery mildew disease in mango.
Powdery mildew disease is one of the most dangerous diseases that affect mango trees. Powdery mildew disease in mango affects all parts of the plant above the surface of the earth, including leaves, flowers, and new growths, as well as small fruits.
The disease of powdery mildew in mango is found intermittently or in an epidemic manner, causing severe losses that may reach 20% of the crop, sometimes rising to 70-80% of the crop at the level of one tree, when it is neglected to combat it, especially when it affects flowers and young mango fruits.
The severity of infection also varies according to the cultivar, for example, the Kent and Alphonse mango cultivars are highly susceptible, while the Tommy Inkins cultivar is less susceptible.
The fungus that causes powdery mildew in mango is Oidium mangifera.
* Powdery mildew mostly affects all cultivated mango varieties, where the secondary infection is during the season through conidia spores in the air, while the fungus spends the period between season and the other in the form of a resident mycelium in the buds, which activates when the appropriate conditions are available to renew the infection.
* Conidia spores of the fungus germinate at a temperature of 23 degrees Celsius in the absence of water and within 5-7 hours when there is a relative humidity of up to 20%, then the optimal development of the disease and its spread occurs in a temperature range between 10-32 degrees Celsius and a relative humidity of 60 – 90%.
Symptoms of powdery mildew in mango trees.
1- Presence of minute white superficial spots of mycelium of mushrooms and the carriers of the conidia that carry barrel-shaped conidia spores (under the microscope) in chains on the modern leaves and flowers of the lateral growths of the flowering and small fruits.
2- When the flowers are infected before they open, mushroom growths appear first on the sepals of the cup, then the small fruits are infected and fall off.
3- The discoloration of the small infected flowers and fruits in a bluish-crimson color, which later turns to brown with the progression of the infection as a result of the death of the affected tissues. Old leaves are rarely infected.
4- The appearance of faint traces on the ripe and immature fruits that were infected in their young stages and then continued to grow.
Control of powdery mildew disease in mango.
1 – Bombing the early flowering sprouts and not allowing the presence of any shamrocks on the trees before the first of February of each year, as they serve as traps for powdery mildew and their removal leads to the emergence of more than one flowering shamrock at the top of the branch as it contains a very high percentage of male flowers. .
2 – Preventive spraying with micronized sulfur when flowering buds swells from mid-February until March at a rate of 250 g/100 liters of water, provided that the spraying takes place in the early morning or evening after four o’clock in the evening.
3- The spraying with micronized sulfur is repeated every 15 days as long as the symptoms do not appear, provided that the spraying is stopped when the air temperature rises, and the spraying must continue at the time of flowering and contract while reducing the pressure of the motor, as the flowering stage is the most vulnerable to infection, and full spraying must also be washing trees .
4- When the infection appears or appears, the spraying with micronized sulfur should be stopped to start spraying with one of the recommended systemic pesticides in exchange, and the spraying with one pesticide should not be repeated twice in a row. The most important pesticides are the following:
* Belartop M70 WP insecticide at a rate of 60 g / 100 liters of water.
* Betazole insecticide 10 EC% at a rate of 25 cc/100 liters of water.
* Amistar pesticide 25% at a rate of 45 cc / 100 liters of water.
* Dovex pesticide 50% SC at a rate of 25 cc / 100 liters of water.
* Crown pesticide 25% SC at a rate of 15 cubic centimeters/100 liters of water.
* Vectra pesticide 10% SC at a rate of 40 cc/100 liters of water.
* Amistar Top pesticide 32.5% SC at a rate of 45 cc/100 liters of water.
Taking into account the different mode of action. Bi-purpose pesticides are preferred to combat blight and powdery mildew.
* To increase the efficiency of spraying, a diffuser is added such as Triton B 1956 or a super film at a rate of 50 cubic centimeters / 100 liters of water.
* Commitment to the recommended concentrations to avoid the occurrence of phytotoxicity and the formation of strains of mushrooms that resist pesticides or reduce their effectiveness.
* Do not mix systemic (therapeutic) pesticides with each other or with any insecticides or foliar fertilizers.
* Use high-pressure spray motors and ensure the validity of the motor tip.