Downy Mildew: Urgent! How to Save Your Plant
Downy mildew is a fungal-like disease caused by oomycetes (water molds) that thrives in cool, wet conditions. It affects a wide range of plants, causing yellowing leaves with fuzzy white-gray growth underneath, leading to defoliation and reduced yields if left untreated.
Fast
14 days
🔍 Symptoms
Main Symptoms
- ! Small green or yellow translucent spots on leaves
- ! Yellow to brown irregular patches on upper leaf surfaces
- ! White, gray, or purple fuzzy growth on leaf undersides
- ! Leaf yellowing, curling, and distortion
- ! Premature leaf drop
- ! Stunted growth in severe cases
Visual Signs
❓ Possible Causes
- → Oomycete pathogens (Peronospora, Plasmopara, Pseudoperonospora species)
- → Cool temperatures (15-23°C / 59-73°F)
- → High humidity above 85%
- → Prolonged leaf wetness from rain, irrigation, or dew
- → Poor air circulation and overcrowding
- → Spread via airborne spores, water splash, contaminated tools
💊 Treatment
Quick Fixes
~7 days
Remove and destroy all infected plant parts. For severe infections, remove entire plant.
Remove and destroy all infected plant parts. For severe infections, remove entire plant.
Apply copper-based or chlorothalonil fungicide to all plants (infected and nearby). Cover leaf undersides thoroughly.
Apply copper-based or chlorothalonil fungicide to all plants (infected and nearby). Cover leaf undersides thoroughly.
Monitor for spread. Improve air circulation by spacing plants and pruning dense growth.
Monitor for spread. Improve air circulation by spacing plants and pruning dense growth.
Second fungicide application. Rotate to different chemical class if available (e.g., mancozeb).
Second fungicide application. Rotate to different chemical class if available (e.g., mancozeb).
Assess progress. Continue weekly fungicide applications until 2 weeks after symptoms disappear.
Assess progress. Continue weekly fungicide applications until 2 weeks after symptoms disappear.
Materials needed:
Organic Treatment
~14 days
Remove all infected leaves immediately and dispose (burn or bury). Disinfect pruning shears between cuts.
Remove all infected leaves immediately and dispose (burn or bury). Disinfect pruning shears between cuts.
Apply neem oil spray to all plant surfaces, especially leaf undersides. Spray in early morning or evening.
Apply neem oil spray to all plant surfaces, especially leaf undersides. Spray in early morning or evening.
Apply baking soda solution (1 tbsp per gallon water) to raise leaf pH and inhibit pathogen growth.
Apply baking soda solution (1 tbsp per gallon water) to raise leaf pH and inhibit pathogen growth.
Prune overcrowded areas to improve air circulation. Water only at soil level in morning.
Prune overcrowded areas to improve air circulation. Water only at soil level in morning.
Reapply neem oil spray. Check for new infections and remove affected leaves.
Reapply neem oil spray. Check for new infections and remove affected leaves.
Apply beneficial microbes (Trichoderma or Bacillus) to soil and foliage to suppress pathogen.
Apply beneficial microbes (Trichoderma or Bacillus) to soil and foliage to suppress pathogen.
Final inspection. Continue preventative measures: proper spacing, morning watering, weekly monitoring.
Final inspection. Continue preventative measures: proper spacing, morning watering, weekly monitoring.
Materials needed:
Expert Treatment
~21 days
Comprehensive assessment: identify pathogen species, measure humidity, check irrigation system. Remove all infected tissue.
Comprehensive assessment: identify pathogen species, measure humidity, check irrigation system. Remove all infected tissue.
Apply systemic fungicide (oxathiapiprolin) as curative treatment. Ensures internal pathogen control.
Apply systemic fungicide (oxathiapiprolin) as curative treatment. Ensures internal pathogen control.
Install or adjust drip irrigation to eliminate leaf wetness. Water only in morning at soil level.
Install or adjust drip irrigation to eliminate leaf wetness. Water only in morning at soil level.
Strategic pruning for airflow. Remove lower leaves if needed. Space plants wider if possible.
Strategic pruning for airflow. Remove lower leaves if needed. Space plants wider if possible.
Apply contact fungicide (copper or chlorothalonil) as protective barrier. Rotate from systemic.
Apply contact fungicide (copper or chlorothalonil) as protective barrier. Rotate from systemic.
Introduce beneficial microbes (Trichoderma + Bacillus) to soil and foliage for biological control.
Introduce beneficial microbes (Trichoderma + Bacillus) to soil and foliage for biological control.
Second systemic fungicide application. Monitor humidity levels and maintain below 85%.
Second systemic fungicide application. Monitor humidity levels and maintain below 85%.
Apply contact fungicide. Check for resistance breakdown. Sample leaves for lab confirmation if needed.
Apply contact fungicide. Check for resistance breakdown. Sample leaves for lab confirmation if needed.
Final assessment. Establish preventative schedule: alternate systemic/contact fungicides every 10-14 days during high-risk periods.
Final assessment. Establish preventative schedule: alternate systemic/contact fungicides every 10-14 days during high-risk periods.
Step by Step
- 1
Identify disease early by checking leaf undersides
- 2
Remove all infected leaves and dispose properly (burn or bury)
- 3
Apply organic or chemical fungicide immediately
- 4
Improve air circulation through spacing and pruning
- 5
Reduce leaf wetness: water at soil level in morning
- 6
Monitor plants daily for new infections
- 7
If severely infected, remove entire plant to protect others
🧪 Solutions
🌱 Natural Solutions
- ✓ Neem oil spray to suffocate pathogens
- ✓ Baking soda solution (1 tbsp per gallon) to raise leaf pH
- ✓ 3% hydrogen peroxide spray for direct pathogen elimination
- ✓ Beneficial microbes: Trichoderma harzianum, Bacillus subtilis
- ✓ Remove and destroy infected leaves immediately
- ✓ Improve ventilation and reduce humidity
💉 Chemical Solutions
- ✓ Copper-based fungicides (Bordeaux mixture)
- ✓ Chlorothalonil
- ✓ Mancozeb
- ✓ Oxathiapiprolin
- ✓ Apply preventatively, rotating chemical classes
- ✓ Follow label instructions carefully
🛡️ Prevention
- ✓ Choose resistant plant varieties when available
- ✓ Space plants widely for better air circulation
- ✓ Use drip irrigation instead of overhead watering
- ✓ Water in the morning to allow leaves to dry quickly
- ✓ Prune plants to improve airflow
- ✓ Practice crop rotation annually
- ✓ Remove infected debris at season end
- ✓ Disinfect tools between uses
- ✓ Avoid working with wet plants
