Aphids on strawberry: crop damage

From strawberry crinkle virus to mild yellow edge virus, find out which aphid species cause which kind of crop damage and when.

Aphid species cause different types of crop damage. All species weaken the plant by ingesting sap and excreting honeydew that contaminates the foliage, flowers and fruits. Sooty moulds may grow on the honeydew, causing blackening. Fruits and/or the calyx may be contaminated by aphids themselves, their dead bodies or their cast skins. The different species infest the plants in different ways and may cause very different symptoms of plant distortion. 

Strawberry aphid

Strawberry aphids do not distort the foliage, but they do make them sticky with honeydew. This species is most important as a potential virus vector (crinkle and yellow edge virus diseases – see Virus-related damage).

Potato aphid

Potato aphids occur very commonly in strawberry, especially in spring, but cause less direct damage to strawberry than other species. Very heavy infestations will weaken the young shoots, contaminate them with honeydew and reduce yield.

Melon and cotton aphid

Melon and cotton aphids attack foliage and flowers, forming dense colonies in patches which produce copious secretions of honeydew which rapidly become blackened by sooty mould. This aphid can also transmit mottle virus.

Glasshouse-potato aphid 

This aphid species causes little direct plant damage to strawberry.

Shallot aphid

Shallot aphids feed during winter and early spring, mainly in the growing points and young leaves, causing strong plant distortion symptoms.

Affected plants become severely stunted when growth commences in spring, the petioles being shortened and the leaves curled and twisted (see below).

Blossom trusses on damaged plants are similarly affected, cropping is much reduced and fruits are small and of poor quality. The symptoms tend to appear first on individual plants or in small patches, but damage soon spreads until large areas are affected. Some growers mistake the damage for that caused by tarsonemid mite (see AHDB Factsheet 02/18). 

Shallot aphid damage to strawberry

Image copyright NIAB EMR.

Several aphid-borne viruses infect strawberry, but the major ones in Europe are strawberry crinkle virus, strawberry mottle virus, strawberry vein banding virus and strawberry mild yellow edge virus. Modern strawberry varieties tend not to show obvious symptoms when infected with one of these aphid-borne viruses. However, the viruses often occur in complexes and cause distortion of plant parts, which may render fruit unmarketable.

Since no practical treatments to cure virus-infected plants are available to the grower, virus diseases of strawberry are predominantly controlled though the use of virus-free planting material, together with control programmes for their transmitting vectors, particularly aphids.

Strawberry aphids, and melon and cotton aphids, transmit virus diseases. Aphicides need to control the aphids rapidly and ideally have a strong repellent and/or anti-feeding effect to help reduce virus transmission. Once a strawberry plant is infected with virus, it remains so for the rest of its life, acting as a source of further infection.