Powdery Mildew – A Disease In Winter Crops To Cause Crop Losses

Are your crops often falling victim to relentless losses every winter, due to some persistent and troublesome powdery growth?  

The root cause of this problem is Powdery mildew disease. Powdery mildew poses a substantial threat to your crops in cool and humid weather conditions prevalent in winter season, putting your yield at risk and causing significant losses. It can cause yield loss of about 20 – 40%, depending upon the intensity of infection. But don’t fear, we’re here to arm you with the knowledge and strategies to control this disease. Look out for visual signs to identify the fungus and take proactive steps at the right time to combat it and safeguard your crop.  

Powdery Mildew Causing Pathogens:

Some common powdery mildew fungi that cause the disease in different crops:

• Podosphaera leucotricha: Apple, pear
• Sphaerotheca fuliginea: Cucurbits, beans, peas, lettuce
• Erysiphe graminis: Wheat, barley, oats, rye
• Sphaerotheca pannosa: Rose
• Leveillula taurica: Chilli, eggplants, tomatoes, castor, red gram
• Uncinula necator: Grapevines
• Erysiphe cruciferarum: Cabbage, cauliflower, mustard
• Erysiphe cichoracearum: Bhendi, tobacco, sunflower, sesame, gourds
• Erysiphe polygoni: Cabbage, carrot, beet root black gram, green gram, peas, beans, coriander, lentils
• Oidium sp: Papaya, chrysanthemum.

Spot Powdery Mildew Symptoms in field:

• Small, water-soaked spots appear on the undersides of leaves, eventually transforming into powdery patches of mycelium and spores.
• Typically, the infections are focused around the leaf veins.
• Infected leaves may exhibit curling or distortion, causing them to appear deformed.
• As the disease progresses, the affected leaves turn necrotic and give ‘scorched appearance’. In severe cases, the leaves may dry up and eventually fall off.
• Affected plants show stunted growth, resulting in smaller and underdeveloped fruits or vegetables.
• The powdery growth on leaves can interfere with the plant’s ability to carry out photosynthesis effectively. This can lead to a decline in overall plant vigor.
• On immature fruit, the mildew initially manifests as circular patches of white mycelium and spores, which can merge together and cover the entire fruit surface.
• During the ripening stage, the fungus may vanish, leaving behind grey scars on fruits. These scars hinder the growth of the underlying tissue, causing deformities in the fruit.

What factors cause this infection in crops?

• The fungus thrives in cool temperatures ranging from 15°C to 25°C, which are often experienced during the winter season in India. Additionally, the relatively dry weather conditions during this period create an ideal environment for the fungus to flourish.
• Dry humid weather following rainfall creates favorable conditions for the growth and spread of powdery mildew.
• Dense planting, overcrowding, or inadequate spacing between plants can obstruct air circulation, creating a more conducive environment for the disease to thrive.
• Weak or stressed plants are more susceptible to powdery mildew infection. Factors such as nutrient deficiencies, improper irrigation, waterlogging, or other environmental stresses weaken the plants’ natural defenses, making them more vulnerable to the fungus.
• Reduced sunlight during winter months can create shaded areas in the crop canopy, providing a favorable environment.
• Infected plant debris or residues from previous crops can serve as a source of inoculum for new infections in winter crops.

Preventive Measures:

• Use powdery mildew resistant or tolerant varieties like Balwant bottle gourd, GS-10 Pea Seed, Sarpan F1 Hybrid Ridge Gourd, Urja Harita Pea Seeds.
• Ensure adequate spacing between plants to promote good air circulation.
• Avoid overhead irrigation to minimize the leaf wetness.
• Remove the crop debris and weeds in the field to reduce the chances of over-wintering spores.
• Early planting can help to reduce the peak season infection.
• Prune the plants to increase air movement and light penetration.
• Apply balanced fertilizers to the crops to increase their ability to tolerate disease.
• Remove and destroy the fallen and affected leaves.

Measures to control Powdery Mildew in crops:

(Follow product’s label to know the right time of application) 

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