Peronospora destructor

Fungal Disease

Peronospora destructor

Fungal Disease

Peronospora destructor

Fungal Disease

Peronospora destructor

Fungal Disease

Peronospora destructor

Fungal Disease

Peronospora destructor is a significant pathogen affecting Allium species, such as garlic and onion. Here’s a concise overview of its characteristics and impact:

1. Host Specificity:

   • Peronospora destructor exclusively infects species in the genus Allium, including garlic and onion.
   • The pathogen thrives and produces spores only in live host plants.

2. Survival and Initial Sources:

   • While it primarily grows in living plants, it can survive in plant debris or soil.
   • Initial sources of infection may include infected bulbs, sets, seeds, and remnants of plant debris from previous crops.

3. Environmental Requirements:

   • Downy mildew has specific environmental requirements, needing both cool temperatures and high humidity for optimal growth.
   • Spore production occurs at or above 95% relative humidity in the plant canopy.

4. Temperature Sensitivity:

   • Spore production declines at temperatures above 24°C and can be suppressed completely if temperatures remain above 82°F (28°C) for more than four hours or above 29°C for more than two hours.
   • Nightly rainfall can also inhibit spore production.

5. Airborne Spores and Infection:

   • Spores are airborne and, upon landing on healthy plants, require leaf wetness to initiate infection.
   • The length of necessary leaf wetness for infection is directly related to air temperature:
     • At temperatures of 6° to 16°C, only 2 to 3 hours of leaf wetness are needed.
     • At 16° to 20°C, infection requires at least 5 hours of leaf wetness.

6. Epidemic Potential:

   • The time between initial infection and sporulation can range from 8 to 16 days.
   • Spores produced overnight can infect new plants the following morning and up to three days later.
   • Under favorable conditions, downy mildew can rapidly escalate into a damaging epidemic, highlighting the need for vigilant monitoring and management strategies.

Understanding the specific requirements and behaviors of Peronospora destructor is crucial for effective disease management in garlic and onion crops. Growers should focus on maintaining optimal growing conditions and promptly addressing any signs of infection to mitigate the risk of outbreaks.