Phytophthora bilorbang root rot

Phytophthora bilorbang is a soil-borne oomycete pathogen known to cause root rot and stem lesions in susceptible host plants. First identified in Australia, this pathogen is part of a complex group of Phytophthora species that are major threats to both natural ecosystems and horticultural operations, particularly in regions prone to high humidity.

The primary hosts of this pathogen belong to the Myrtaceae family, including various Eucalyptus and Corymbia species. P. bilorbang specifically targets the root systems, compromising the plant's ability to uptake water and essential minerals, which is particularly devastating for young saplings and nursery-grown trees.

Symptoms of the infection typically include leaf yellowing (chlorosis), wilting, and dieback of the canopy. Below ground, the pathogen destroys the fine feeder roots, causing them to turn dark and necrotic. If the infection reaches the base of the stem, it can result in cankers that may eventually girdle and kill the host.

The development and spread of Phytophthora bilorbang are largely dependent on environmental conditions, particularly soil moisture and temperature. Zoospores, which are motile spores, travel through water films in the soil, allowing the pathogen to infect neighboring plants efficiently, especially when drainage is poor or irrigation is excessive.

Management strategies focus on rigorous hygiene protocols to prevent the introduction of the pathogen into new areas.

• Implement strict quarantine for new plant stock.
• Ensure excellent soil drainage and aeration.
• Sanitize tools and equipment regularly.
• Apply phosphite-based treatments when necessary.
• Remove and destroy symptomatic plants promptly.