Plant problems

Why Are My Strawberry Leaves Curling?

Q: What is strawberry leaf scorch?

Strawberry leaf scorch (Diplocarpon earliana; syn. Marssonina fragariae) is a fungal disease of strawberry that is very common in UK gardens in wet, warm summer conditions and in closely spaced plantings with poor air circulation; it is one of several fungal diseases that can cause leaf browning, spotting, and curling in UK-grown strawberries alongside strawberry leaf spot (Mycosphaerella fragariae, now Ramularia fragariae) and strawberry powdery mildew (Podosphaera aphanis). Symptoms of leaf scorch: the first symptoms of Diplocarpon earliana leaf scorch are small, irregular, dark red-purple to dark brownish-red spots or patches on the leaves; the spots may initially have a slightly purplish or reddish border; as the disease progresses, the spots expand and can coalesce; the tissue between the expanding spots turns yellow and eventually becomes pale brown and dead; the leaves can appear scorched, with large areas of dead and dying tissue; the leaves may curl, dry, and die completely in a severe infection; the disease affects the older leaves of the plant most severely; it is most common from June to September in wet UK summer conditions. Management: promptly remove and dispose of the most severely affected leaves to reduce the local source of spores; do not compost diseased leaf material; ensure adequate spacing between plants (at least 30 to 45 cm) for good air circulation; avoid overhead watering (water at the soil level) as wet foliage promotes fungal disease spread; mulching the strawberry bed with straw or black polythene sheeting reduces soil splash onto the lower leaves and also helps keep the fruit clean and reduces soil-borne disease transfer; copper-based fungicide sprays and some registered fungicide products are available in the UK for use on strawberry leaf diseases; check current UK product registrations (products registered for amateur garden use change from year to year) and always follow product label instructions for use on edible crops.

Fragaria x ananassa (garden strawberry) is the most widely grown fruit in UK domestic gardens. The trifoliate leaves curl, crinkle, or show distinctive notched margins most often from strawberry aphids (pale, small, and easy to miss, but very efficient virus vectors); from vine weevil larvae destroying the root system in containers (sudden wilting despite moist compost is the diagnostic sign); from strawberry viruses transmitted by the aphid; or from leaf scorch in wet UK summers.

Strawberry aphids

Chaetosiphon fragaefolii is a strawberry-specific aphid; it is particularly damaging as a very efficient vector of several serious strawberry viruses rather than for its direct feeding damage. The colonies are pale yellow-green, small, and relatively inconspicuous; check the growing points and undersides of the youngest leaves. Aphid feeding and virus transmission together cause leaf curling, crinkling, yellow marginal banding, reduced vigour, and reduced fruit production.

What to do

Check the growing points and youngest leaf undersides regularly from April to June for the pale yellow-green aphid colonies; squash or rub off colonies with fingers; encourage natural predators (ladybirds, lacewing larvae); avoid insecticide use that kills natural predators; if chemical control is needed for culinary strawberries, check the edible crop withholding period on the product label; the most important long-term protection against strawberry viruses is starting with certified disease-free plants and replacing plants every three to four years.

Vine weevil

Otiorhynchus sulcatus is one of the most serious pests of container-grown strawberries. The diagnostic sign of larval damage: a container strawberry suddenly wilts and collapses even when the compost is moist. The adult cuts very characteristic irregular scalloped notches from strawberry leaf margins at night; this distinctive notch damage is a reliable early warning sign of adult vine weevil activity. Both the adults and the cream C-shaped larvae are readily identifiable.

What to do

Tip the plant out of its container in September to October and inspect the compost and root ball for cream-coloured C-shaped larvae; remove and destroy any found; replace all the compost before repotting; apply entomopathogenic nematodes (Steinernema kraussei, effective above approximately 5°C; or Heterorhabditis bacteriophora, effective above approximately 12°C) watered into moist compost in late summer (August to October) as a preventative and as a treatment; both are widely available from UK biological control suppliers; strawberries grown in the open ground are less susceptible to vine weevil than container-grown plants.

Strawberry viruses

Multiple viruses transmitted primarily by the strawberry aphid (Chaetosiphon fragaefolii) affect UK strawberry plants. Strawberry crinkle virus: leaves severely crinkled, puckered, and distorted; plant stunted and unproductive. Strawberry mild yellow edge virus: leaf margins turn pale yellow to cream giving a characteristic yellow edge or halo. Strawberry mottle virus: subtle mottling and pale yellow-green mosaic patterns. There is no cure; infected plants should be removed.

What to do

Remove and destroy virus-infected plants (dispose of in general waste; do not compost); do not use runners from virus-infected parent plants for propagation as the daughter plants will carry the virus; replace with certified disease-free plants from a reputable UK specialist strawberry nursery (certified plants have been propagated from mother plants tested and confirmed free of the major strawberry viruses); control strawberry aphids rigorously to reduce virus transmission risk.

Leaf scorch

Diplocarpon earliana (leaf scorch) causes small, irregular, dark red-purple spots or patches on leaves; spots expand and coalesce; tissue between spots turns yellow then pale brown and dead; leaves may curl, dry, and die completely in severe infections. Most common in wet UK summer conditions from June to September in closely spaced plantings with poor air circulation.

What to do

Remove and dispose of the most severely affected leaves in general waste (not compost); ensure adequate spacing between plants (at least 30 to 45 cm) for good air circulation; avoid overhead watering; water at soil level; mulch the strawberry bed with straw or black polythene sheeting to reduce soil splash onto the lower leaves; copper-based fungicide sprays and some registered fungicide products are available in the UK for strawberry leaf diseases; check current UK product registrations and follow product label instructions for use on edible crops.

Frequently asked questions

Why are my strawberry leaves curling?

Strawberry leaves curl most commonly because of strawberry aphids (Chaetosiphon fragaefolii; strawberry-specific aphid; particularly damaging as very efficient vector of several serious strawberry viruses; colonies pale yellow-green small and relatively inconspicuous; check growing points and youngest leaf undersides from April to June; squash or rub off by hand; encourage natural predators; start with certified disease-free plants and replace every 3 to 4 years as most important long-term protection), vine weevil (Otiorhynchus sulcatus; most serious pest of container-grown strawberries; diagnostic sign of larval damage: sudden wilting and collapse despite moist compost; adult cuts characteristic irregular scalloped notches from leaf margins at night; tip plant out of container in September to October and inspect for cream C-shaped larvae; remove and destroy; replace all compost; apply Steinernema kraussei nematodes to moist compost in August to October; effective above approximately 5°C), strawberry viruses (multiple viruses transmitted primarily by strawberry aphid; strawberry crinkle virus: leaves severely crinkled puckered and distorted; strawberry mild yellow edge virus: leaf margins turn pale yellow to cream; strawberry mottle virus: subtle mottling; no cure; remove and destroy infected plants; do not compost; do not use runners from infected plants; replace with certified disease-free plants), or leaf scorch (Diplocarpon earliana; dark red-purple spots on leaves; spots expand and coalesce; tissue between spots turns yellow then pale brown and dead; most common in wet UK summer conditions from June to September; adequate spacing; water at soil level not overhead; straw or black polythene mulch; copper-based fungicide or registered fungicide products for strawberry leaf diseases).

How do I control vine weevil on strawberries?

Adult vine weevil detection: small (8 to 9 mm) dull greyish-black flightless beetle with distinctive curved snout and elbowed antennae; nocturnal; very characteristic irregular scalloped-notch damage (approximately 2 to 4 mm deep with curved not straight margin) on strawberry leaf margins reliable early diagnostic sign of adult vine weevil activity; a strong warning that larvae are likely to be present in compost or soil later in the season. Larval detection and treatment: tip the strawberry plant and compost out of container in late summer (September to October) and examine compost and root ball carefully for cream-coloured legless C-shaped vine weevil larvae; typically found at bottom of pot and around edge of root ball; remove and destroy any found by hand; replace compost entirely before repotting. Biological control: Steinernema kraussei (effective at soil temperatures above approximately 5°C; can be applied in early spring and late autumn) or Heterorhabditis bacteriophora (effective above approximately 12°C; most effective in warm UK summer conditions June to September); both available by mail order from UK biological control suppliers and from some UK garden centres; apply as suspension watered into moist compost around base of plants; best time to apply late summer (August to October) when newly hatched larvae are smallest most vulnerable and closest to soil surface. Growing in the ground: strawberries grown in open ground in well-drained strawberry bed less susceptible to vine weevil damage than container-grown plants; moving container strawberries into open ground or raised bed reduces vine weevil risk.

How long do strawberry plants last in the UK?

Productive lifespan: a well-grown UK garden strawberry plant is most productive in its second and third years (conventionally plants are planted in summer June to August and runners and flowers removed in first season to allow establishment; first full crop harvested in following summer which is year two; this is typically most productive year; year three second full crop also very productive; from year four onward yield of most varieties begins to decline as crown becomes woody and virus infection accumulates; replace plants every 3 to 4 years to maintain consistently high yields). Runners: most summer-fruiting varieties produce runners (stolons) in summer; each runner produces rooted plantlets at intervals; these daughter plants are genetically identical clones; pin down onto a small pot of compost close to parent plant; tip plantlet roots into compost within 3 to 4 weeks; once well-rooted sever from parent runner and grow on; plant out rooted runner plants July to September; do NOT use runners from virus-infected parent plants for propagation as daughter plants will carry the virus. Certified disease-free plants: replacing with certified disease-free plants from reputable UK specialist strawberry nursery gives best disease-free start; certified plants propagated from mother plants tested and confirmed free of major strawberry viruses; reduces risk of introducing virus-infected plants into the garden.

What is strawberry leaf scorch?

Diplocarpon earliana (syn. Marssonina fragariae) is a fungal disease of strawberry very common in UK gardens in wet warm summer conditions and in closely spaced plantings with poor air circulation; alongside strawberry leaf spot (Ramularia fragariae) and strawberry powdery mildew (Podosphaera aphanis). Symptoms: first symptoms are small irregular dark red-purple to dark brownish-red spots or patches on leaves; spots may initially have slightly purplish or reddish border; as disease progresses spots expand and can coalesce; tissue between expanding spots turns yellow and eventually becomes pale brown and dead; leaves can appear scorched with large areas of dead and dying tissue; leaves may curl dry and die completely in severe infection; affects older leaves most severely; most common June to September in wet UK summer conditions. Management: promptly remove and dispose of most severely affected leaves in general waste (not compost); ensure adequate spacing (at least 30 to 45 cm) for good air circulation; avoid overhead watering; water at soil level; mulch strawberry bed with straw or black polythene sheeting to reduce soil splash; copper-based fungicide sprays and some registered fungicide products available in UK for strawberry leaf diseases; check current UK product registrations and follow product label instructions for use on edible crops.