Strawberry leaf scorch
Diplocarpon earlianum
Small purple spots that run together until the leaf looks burnt and curls at the edges. It weakens the crown over a season rather than killing outright.
What you'll see
- Many small irregular purple spots on the upper leaf surface, without the pale center a leaf spot would have.
- Spots running together until whole areas are purple-brown and the leaf looks scorched.
- Leaf margins curling upward and the leaf drying and dying from the edge.
- Purple blotches on the runners, stalks and the caps of the fruit.
- A bed that thins out and crops less each year, with plants going into winter half-defoliated.
Why it happens
A fungus that overwinters on the old infected leaves left in the bed and starts again in spring from spores splashed up onto the new growth. It is favored by everything that keeps a strawberry leaf wet — dense matted rows, low airflow, and overhead watering — and it builds year on year in a bed that is never renovated.
Warm, wet weather from spring onward, and thick matted plantings. Beds in their third or fourth year without renovation carry the worst of it, and a wet autumn sends the plants into winter weakened.
Treating it
- Mow or shear the foliage off a June-bearing bed straight after the last picking, rake it away and bin it — the standard renovation, and the most effective control there is.
- Pick off the worst leaves through the season on a small bed or an everbearing cultivar you cannot mow.
- Thin the row to single crowns rather than a solid mat.
- Water at the base in the morning and mulch with clean straw.
- Take out plants that are more scorch than leaf; they will not carry a crop next year.
Keeping it away
- Renovate June-bearing beds every year immediately after harvest.
- Space plants generously and keep runners thinned to an open row.
- Grow resistant cultivars, which differ a great deal.
- Start a new bed on fresh ground every three or four years from clean runners.
- Clear all old leaves from the bed in late winter before growth starts.
See also
The Cottage Garden Companion — the gardener's apothecary at cottagegardencompanion.com