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Pest & Disease Library · Solutions

Downy Mildew Control in Lettuce

Lettuce downy mildew runs in cool, moist, foggy conditions, yellowing leaves and sporulating on undersides. Infected outer leaves must be stripped, cutting yield and pack-out quality.

Common crops affected

Why it matters

It spreads explosively when leaves stay wet, causing severe defoliation and yield loss; prevention ahead of wet weather is essential.

When to act

Protect in cool, humid, foggy periods from early growth.

What to look for

  • Pale-yellow angular patches on upper leaves
  • White-gray sporulation underneath
  • Necrotic older leaves needing removal
  • Downgrade and trim loss at harvest

How to manage it

  1. Improve airflow; avoid overhead watering; water early.
  2. Remove infected leaves.
  3. Apply Spore Control (1:1,000) at first sign and ahead of wet weather.

Recommended Vegalab program

Mildew Control — adherent encapsulated cover for rainfast protection.

RoleProductUse
Primary controlSpore ControlThymol protective fungicide
CompanionMildew ControlWhere mildews dominate
Plant resilienceArmour BoostResilient tissue

Product claims, rates, and availability vary by jurisdiction; always follow the applicable label.

Frequently asked questions

Does variety choice help?

Resistant varieties help but races shift — combine with preventive cover and airflow.