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Strawberry leaf spot: how to recognise and treat it

Disease

Strawberry leaf spot — Photo: Michal Maňas, CC BY 2.5, Wikimedia Commons

Symptoms

Small round dark-purple spots on the upper side of the leaves.
The spots grow to 3–6 mm; their centre turns brown, then grey or white, with a sharp purple-red border.
Many spots merge and the leaf dies.
Elongated spots on leaf stalks, runners, flower stalks and the green caps of the berries.
Plants lose vigour and the crop is smaller and poorer.

Organic treatment

When only a few plants show spots, remove them early, before the fungus spreads.
After harvest, clear old strawberry leaves and debris and dispose of them away from the bed.
If the disease is widespread, spray a copper fungicide, Bordeaux mixture or Bacillus subtilis when the first three or four new leaves unfold; follow the label dose.

Chemical treatment

Captan or myclobutanil when the first new leaves unfold; alternate products for a second spray two weeks later in wet weather, because the fungus can become resistant. Check the product is approved for strawberries in your country and follow the label dose and pre-harvest interval.

Reference information, not a guarantee. Read and follow the label of any product: dose, safety and the days to wait before harvest.

Prevention

Buy disease-free plants and reject any with leaf spots.
Plant in a sunny, open spot, do not crowd the plants and keep weeds down for good airflow.
Water with drip or at the base; if you water from above, do it in the morning so leaves dry quickly.
Do not feed young plants heavily with nitrogen — soft new leaves are the most easily infected.
Choose resistant varieties where they are offered.

Plants it affects

Strawberry

Sources

Figures checked against these sources.