Aphids Are Attacking My Strawberry Plants

The strawberry aphid (Chaetosiphon fragaefolii) is a small, pale yellow-green aphid that colonises the underside of young leaves, causing them to curl inward and distort as the colony grows. Unlike the dramatic jet-black or grey colonies seen on broad beans and brassicas, strawberry aphid infestations tend to be subtle — the curled leaf hides the colony. The damage itself is mild; the serious concern is that the strawberry aphid is the primary vector for the suite of viruses that progressively weaken strawberry plants over years. A garden with high aphid pressure year after year will accumulate virus in its plants.

Identifying the infestation

Leaf curling on young, actively growing strawberry leaves is the first symptom — gently uncurl a distorted leaf and look for clusters of tiny pale aphids on the underside, along the midrib and in the folds. Honeydew (sticky excretion) may be visible on leaf surfaces below a large colony. Early in the season, colonies are small and often missed. Check young growth regularly from April onward when aphid populations begin building.

Direct control

Crush small colonies by hand when found early in the season. A jet of water directed at the leaf underside dislodges aphids effectively, though colonies rebuild within a week if aphids have not been completely removed. Insecticidal soap spray applied to the leaf underside is effective at killing aphids on contact. Repeat after rain. Neem oil mixed with water and a small amount of liquid soap is a longer-lasting contact deterrent. Avoid any broad-spectrum insecticide during the flowering period — these kill bees and other pollinators.

Virus management through plant renewal

If your strawberry plants are more than three years old and showing yellowing, mottling, or distortion in the leaves alongside aphid presence, the plants are likely virus-infected. No amount of aphid control will restore virus-infected plants. Renew the entire bed with certified virus-free plants from a reputable supplier, planted in a fresh site at least two metres from the old bed. New clean plants, combined with ongoing aphid management, will give you another three to four virus-free seasons.