Phytophthora root rot of acacia

The disease is caused by the oomycete Phytophthora acaciae, which acts as a soil-borne pathogen targeting the root system. This Phytophthora root rot disrupts the plant's vascular system, preventing the effective transport of water and nutrients from the soil to the canopy.

The primary hosts are various species of acacia (Acacia spp.). In nursery settings and ornamental landscapes, these trees are particularly susceptible if their physiological health is compromised by poor planting practices or environmental stress.

Symptoms initially appear as subtle crown thinning, yellowing foliage (chlorosis), and wilting during dry periods. Advanced stages of infection reveal brittle, decayed roots with necrotic lesions that often extend to the root collar, eventually leading to tree mortality.

The development and dissemination of the disease are highly dependent on moisture. Saturated soil conditions facilitate the production and movement of motile zoospores, which travel easily through waterlogged ground or surface runoff to reach healthy host roots.

Managing the disease is challenging once systemic infection occurs, making preventive measures the most effective strategy.

• Ensuring proper soil drainage to avoid waterlogged zones.
• Avoiding excessive irrigation around the root collar.
• Using certified, disease-free nursery stock for planting.
• Applying targeted fungicidal treatments containing phosphonates or metalaxyl as needed.