Phytophthora root rot of strawberry

The causal agent of Phytophthora root rot is the oomycete Phytophthora fragariae. It is a devastating soil-borne disease that targets the root system of berry crops, leading to significant physiological stress, nutrient deficiency, and eventual death of the plant.

The primary hosts of this pathogen are strawberries and raspberries. The disease thrives in saturated soil conditions, as the pathogen produces motile zoospores that require water to swim and reach the root cortex of healthy neighboring plants.

Early symptoms include stunted growth and the development of reddish or purplish leaves, which often wither during warm periods. A definitive diagnostic feature is the necrosis of the vascular cylinder within the root, which appears dark brown while the outer root tissue might initially remain white.

The development of the fungus is highly favored by cool and damp weather. It spreads rapidly through contaminated irrigation water, infested soil clinging to machinery, or infected nursery stock, which is the most common way for the disease to enter a new planting site.

The economic impact of Phytophthora root rot is severe, as it can decimate entire fields within a very short time. Because the pathogen produces long-lived oospores that can survive in the soil for several years, eradication is extremely difficult once a site is infected.

Effective management strategies include:

• Planting only certified, disease-free nursery stock.
• Ensuring well-drained soil and avoiding irrigation water accumulation.
• Implementing strict crop rotation programs (5–7 years before replanting).
• Applying appropriate fungicides as a preventive measure in high-risk areas.
• Prompt removal and destruction of infected plants and surrounding soil.