Cinnamon fungus

Pathogen and disease type: Phytophthora cinnamomi is a devastating soil-borne oomycete pathogen responsible for root and crown rot. It attacks the vascular system of plants, effectively cutting off water and nutrient uptake, which leads to physiological decline and eventual death of the host.

Host range: The pathogen has an exceptionally broad host range, infecting over 4,000 species of plants worldwide. Major susceptible crops include avocado, pineapple, macadamia, and chestnut. It also severely impacts horticultural species, particularly Ericaceae members like azaleas and rhododendrons, and various woody forest trees.

Symptoms and signs: The earliest symptoms are often subtle, including leaf chlorosis, wilting, and stunted growth. As the root system decays, the plant shows significant dieback of branches. In advanced stages, the foliage turns brown and brittle, and the base of the stem may show lesions, eventually causing the plant to collapse.

Environmental conditions and spread: Phytophthora cinnamomi thrives in warm, moist soil conditions. The pathogen reproduces by producing motile zoospores, which travel through soil water to reach new roots. Spread is further facilitated by human activities, including the movement of infected soil on equipment, vehicles, or through contaminated nursery stock.

Economic impact and management: This pathogen causes significant economic losses in both agricultural and natural ecosystems by destroying plant root systems. Management strategies focus on:

• Implementing strict quarantine and sanitation protocols;
• Improving soil drainage to minimize waterlogging;
• Using pathogen-free nursery stock;
• Applying phosphite-based fungicides to inhibit the spread and boost plant immunity.