Grapes: a season plan for downy and powdery mildew

Downy mildew and powdery mildew are the two diseases that cost Nashik grape growers the most. Downy mildew spreads explosively in warm, humid weather after rain or heavy dew; powdery mildew thrives in dry weather with cool nights. A season plan that prevents infection is far cheaper than trying to cure it after the bunches are affected.

Doses in this guide are taken from the product labels. Always read the label and leaflet before use, respect the pre-harvest interval, and check with your nearest Biostadt retailer or agronomist for advice specific to your field.

Know the enemy

Downy mildew

• Leaves: yellow, oily spots on the upper surface with white downy growth underneath, most visible in the early morning.
• Bunches: young bunches turn brown and dry; berries shrivel and fall.
• Risk weather: leaf wetness for several hours with temperatures of 20 to 25 °C. After rain in the foundation or fruit pruning season, assume infection is starting.

Powdery mildew

• Leaves and berries: white, ash-like powder that rubs off; infected berries crack and stay small.
• Risk weather: dry days, cloudy spells and dense canopy with poor air movement.

Cultural practices come first

• Remove and destroy infected shoots, leaves and dried bunches from the previous season.
• Keep the canopy open: timely shoot thinning, removal of laterals and leaves around the bunch improve airflow and spray penetration.
• Avoid excess nitrogen, which makes soft, dense growth that both mildews love.
• Improve drainage and avoid overhead irrigation. Water in the morning so leaves dry quickly.

Spray plan after fruit (October) pruning

Stage	Main target	Product and label dose
Bud break to 3–5 leaf	Downy mildew (preventive)	Captek 2500 ml/ha or Dolby 300 g per 100 L water
Pre-bloom (bunch elongation)	Downy mildew	Duo guard 1500–2000 ml/ha or Sanchar 2500 ml/ha
Flowering to fruit set	Powdery mildew	Trigger Pro 500–1000 ml/ha or Cygnet 40 g per 10 L water
Berry development	Powdery mildew, anthracnose	Redeem 30 ml per 100 L water or Hitone 2000 ml/ha
After rain at any stage	Downy mildew	Repeat a downy mildew spray within 24–48 hours, rotating to a product not used in the last spray
Before veraison, dry weather	Powdery mildew	Wokovit 1875–2500 ml/ha

Avoid resistance

• Never use the same product more than twice in a row, and no more than two to three times in a season.
• Alternate between products from different groups (for example Captek, Duo guard and Sanchar for downy mildew).
• Use systemic products preventively, not as a last-minute rescue on heavy infection.

Other useful tools

• Dormex (hydrogen cyanamide) after pruning gives uniform bud break, which makes every later spray more effective. Follow the label dose and timing for your variety.
• BioGreen Calcium 2–2.5 ml per litre and BioGreen Boron 1–1.5 ml per litre around flowering and berry set support berry firmness and set.

Spray safely

• Wear gloves, a mask, full sleeves and eye protection while mixing and spraying.
• Spray in the early morning or late evening, never against the wind or before expected rain.
• Use clean water and the full recommended water volume. Poor coverage is the most common reason a spray "does not work".
• Do not mix products unless the label allows it. If unsure, do a jar test first.
• Keep children and animals away, and never reuse empty containers. Rinse them three times, puncture them and dispose of them safely.