Damage

Several virus and virus-like diseases affect strawberries causing varied and complex problems. Infected mother plants pass the virus to their runner plants and, thus, virus related damage is more severe as the planting ages. The damage can seriously reduce vigour and yield. Infected fruit is often small, deformed and poor in flavour.

Symptoms

There are number of viruses and virus-like diseases that have been found in BC. The most common viruses on strawberry are strawberry mottle virus, strawberry mild yellow edge virus, strawberry vein banding virus and strawberry crinkle virus. The symptoms are variable depending on the type of virus or combination of viruses and the strawberry variety. Susceptible varieties like Hood may show stunting, crinkling, yellowing, mottling, and/or leaf curling. More tolerant varieties like Puget Reliance may show few or less symptoms except for stunting and reduced fruit size and yield.

Recently, a new virus complex has occurred in the Fraser Valley. In affected fields symptoms are first seen in the year of planting and progress to cause severe damage in the fruiting years. Beginning with the youngest leaves, the whole plant becomes twisted and severely stunted. Leaves show a distinctive reddening of the veins. Strawberry crinkle virus in combination with other viruses is believed to be involved. Totem and Rainier appear to be particularly susceptible to this condition.

Disease Cycle

Viruses are spread from infected plants to healthy ones mainly by aphids. Strawberry aphids develop wings and are flying before new strawberry fields are planted. They can infect new plants with viruses as soon as the first leaves emerge from the crown. The viruses are then passed to other plants by either winged or wingless aphids as the aphids move about in search of young leaves.

Monitoring

Scout for early symptoms and monitor aphid populations in both established and first year fields and apply sprays as necessary.

Management

Cultural control

Select tolerant varieties. Avoid planting susceptible varieties, such as Hood, close to established plantings of tolerant varieties.

Isolate new plantings from established fields to reduce aphid movement and virus transmission.

Start new plantings from certified stock that was grown to minimize virus infection.

Keep fields free of weeds as they harbour several kinds of aphids that can spread virus diseases.

Chemical control

Control aphids in established fields close to new plantings.

Apply a residual, systemic aphicide when aphids are first detected in a new planting. Apply further aphid control sprays whenever aphids reappear (see also “Aphids” above).