Phytophthora macrochlamydospora rot

Pathogen and disease type. Phytophthora macrochlamydospora is a distinct oomycete pathogen classified within the genus Phytophthora. It is primarily known for causing destructive root and stem rot diseases, significantly impacting plant physiology by obstructing water and nutrient transport throughout the vascular tissues.

Susceptible crops. This pathogen exhibits a broad host range, particularly affecting various herbaceous and woody species. Crops belonging to the Solanaceae and Fabaceae families are especially susceptible, as are certain species of ornamental plants grown in high-humidity nursery environments.

Symptoms and signs of infection. Clinical signs include chlorosis, stunting, and sudden wilting of the aerial parts of the plant. A critical diagnostic indicator is the darkening and decaying of the root crown. In moist environments, a thin, white mycelial growth may appear on the necrotic lesions near the soil surface.

Development and impact. The pathogen thrives in saturated soils and cool-to-moderate temperature regimes. The formation of thick-walled macrochlamydospores allows the fungus to remain dormant in the soil for several years, making the disease difficult to eradicate once it is established in a field or greenhouse.

Control and prevention measures. Effective management requires an integrated pest management strategy.

• Improve soil drainage to eliminate standing water and high humidity.
• Practice long-term crop rotation to reduce the pathogen load in the soil.
• Utilize pathogen-free, certified seeds or transplants.
• Apply preventative fungicides containing copper, metalaxyl, or phosphonates.
• Remove and destroy infected plant debris immediately after harvest.