Red stele
Phytophthora fragariae
also called Red core
Strawberry plants stunted and blue-green, wilting in the first warm spell — and a root sliced lengthways showing a rusty red core. There is no cure.
- Patches of stunted plants in the wettest, heaviest part of the bed, worst in a wet spring.
- Older leaves turning red or yellow early while the young leaves go a dull blue-green.
- Plants wilting and dying on the first warm dry day after a wet spell, as if they had never rooted.
- Roots rotted off to short stubs — the rat-tail root — with no fine feeding roots left.
- A root split lengthways showing a rusty red or brown core running up the middle, in a root whose outside still looks white. This is the diagnosis and nothing else gives it.
A soil-borne water mold specific to strawberry. It produces swimming spores that need free water in the soil to reach a root, and resting spores that survive in the ground for a decade or more. It arrives almost always on infected runners or on soil carried in on boots, tools or a rotavator.
Cold, wet, badly drained soil in autumn, winter and early spring. A heavy clay bed, a low corner, or a bed that floods after rain is where it appears; a raised, free-draining bed rarely sees it at all.
- There is no cure. Pull the affected plants with their roots and bag them.
- Do not replant strawberries in that ground; the resting spores will outlast your patience.
- Move the strawberry bed to fresh, free-draining ground, preferably raised.
- Clean boots, tools and any machinery before leaving the bed, and work it last.
- Do not take runners from an affected bed however healthy they look.
- Buy certified virus- and disease-free runners from a reputable supplier.
- Plant in raised beds or on ridges on any soil that holds water.
- Improve drainage before planting rather than after the plants are in.
- Grow resistant cultivars — Allstar, Earliglow, Sparkle and Guardian among them.
- Rotate the strawberry bed every three or four years onto ground that has not grown them.
Strawberries only. The wild strawberry can carry it without showing much.
The Cottage Garden Companion — the gardener's apothecary at cottagegardencompanion.com