Have you ever noticed yellow spots on leaf or drying of its edges on your grapevines, especially during cool, damp mornings? And when you flip the leaf, have you observed any white or grayish powdery layer underneath? If yes, then your crop may be affected by a disease called Downy Mildew.

Downy mildew is a serious plant disease caused by oomycetes, a group of fungus-like organisms (Often referred as Water molds). It affects many crops by thriving in cool and moist conditions. The symptoms are mainly observed on the leaves but can also affect stems, flowers, and fruits, leading to major yield losses. The fungus causing the disease are usually host-specific (e.g., Plasmopara viticola in grapes, Peronospora destructor in onions). It a major threat in frequent rainfall or densely planted areas. Awareness and early intervention is crucial for sustainable farming.

• Upper leaf surface show small, pale yellow to green, oil-like angular spots limited by leaf veins (In cucurbits).
• On the lower surface of the leaf, white, grey, or purplish downy growth appears beneath yellow spots, often developing overnight in high humidity.
• Later, these yellow spots enlarge and turn brown or necrotic and the downy growth thickens and may spread over a larger area under the leaf.
• Leaves may curl, distort, or show water-soaked lesions.
• In crops like grapes and cucurbits, young shoots or petioles may become infected.
• Affected areas may give off a musty or fungal odor.

Advanced stage of infection

• Premature defoliation with stunted growth in young plants.
• Blighted flowers, shriveled fruits or fruit rot (e.g., grapes, cucurbits).
• In systemically infected crops (like maize or pearl millet), whole plants may become dwarfed, pale, and fail to produce grain or fruit.
• Secondary infections may develop on damaged tissue

Crop-Specific Symptom

Crop	Specific Symptoms
Grapes	Yellow spots on leaves, white downy growth under leaf, fruit rot or shriveling
Cucurbits	Angular yellow spots, grayish mold on leaf underside, fruit cracking or rotting
Onion	Elongated, pale streaks on leaves, leaf bending or collapse, white downy layer
Mustard & Cabbage	Leaf yellowing, purplish mold underside, reduced head/seed formation
Sunflower	Pale leaf spots, systemic stunting, thick mold on lower leaf surface
Sorghum/Millet	Chlorotic stripes, systemic stunting, white sporangial growth

Life Cycle of Downy Mildew

1. Survival Stage (Over seasoning)

2. Spore Germination (Favorable Conditions)

3. Infection Stage (Entry into Host)

4. Colonization and Symptom Development

5. Asexual Reproduction (Spread)

6. Sexual Reproduction (End of Season)

Management and Control Measures

1. Cultural Methods

• Always use certified, disease-free seeds or seedlings to prevent introducing the pathogen.
• Rotate crops with non-hosts to break the downy mildew cycle; avoid planting the same susceptible crop repeatedly.
• Ensure proper spacing and pruning to maximize airflow to reduce disease development.
• Avoid overhead irrigation and use drip irrigation to minimize leaf wetness.
• Remove and destroy infected plants and debris to eliminate sources of infection.
• Adjust planting time to avoid conditions favorable for disease.
• Avoid excessive nitrogen, as it promotes lush growth, which is more susceptible to infection.
• Use organic mulch to reduce soil splash and maintain consistent soil moisture, helping to prevent disease spread.
• Keep fields well-drained to prevent conditions that favor disease spread.

1. Biological methods

• Pre planting application of Multiplex Nisarga or Multiplex Bio-Jodi at 2- 5 Kg/ Acre –to suppress existing downy mildew pathogens surviving in soil.
• A foliar spray of Multiplex Rognash-B at 2–3 ml per liter of water can be applied at early stages of the crop.
• Apply Multiplex Trishul at 4- 8 Kg/ acre to improve nutrient uptake and activate plant defense mechanisms, making crops less susceptible to downy mildew pathogen.

Chemicals measures

• Rotate chemicals with different modes of action to prevent buildup of resistance.
• Fungicides like Nagcoper @ 2-3g/L or Nagziram @ 2–2.5 m/L or SPEED @2-3 g/L or Multiclear @ 3- 4 ml/ L or POP UP @ 2 g/L.
• Combi products like Duo-Care @ 1-1.5 ml/L or M &M @ 2g/L are also effective in controlling downy mildew disease.

• Fungicides application should be taken at the earliest sign of disease and continued at the suggested intervals, as early intervention is vital for effective control and prevention.