Why Are My Strawberry Plants Collapsing With Red Roots?

Strawberry plants that wilt progressively — outer leaves collapsing first, then the whole plant dying back — and on pulling reveal roots that are brown or dead with a characteristic red or red-brown discolouration in the central root core (the stele, visible when you snap a root and look at the cross-section) have red core disease, caused by Phytophthora fragariae. Red core is one of the most serious strawberry diseases in the UK, particularly in cold, wet clay soils where the oomycete pathogen thrives and persists.

How to confirm red core

The defining diagnostic is the red or red-brown stele (central core) visible in infected roots. Pull up an affected plant and select a root that is partially brown. Snap it and look at the cross-section — healthy roots have a white central core; red core-infected roots have a clearly reddish-brown or orange-red central stele. The outer root tissue may still look white (in early infection) while the core is already red. Leaf symptoms typically appear first in late winter or early spring as plants try to grow after cold, wet periods — the roots have been destroyed during winter dormancy and cannot support growth.

Why red core is associated with wet soils

Phytophthora fragariae produces motile zoospores that swim through waterlogged soil to infect strawberry roots. It is most active when the soil is saturated and temperatures are between 5–12°C — precisely the conditions of cold, wet autumn and winter periods. Clay soils, poorly drained sites, and beds in low-lying areas are at greatest risk. Free-draining soil, raised beds, or very well-structured sandy loam significantly reduces the risk of red core infection.

Management and replanting

There is no chemical treatment approved for home garden use against red core. If red core is confirmed in your bed, the immediate action is to remove and destroy affected plants and avoid replanting strawberries in the same area for at least five to seven years — the pathogen survives in soil as thick-walled oospores for many years. Replanting should be in a new, well-drained site with resistant varieties (many modern varieties have partial red core resistance — check descriptions when purchasing). Raised beds offer the best protection in gardens with heavy soil.