Potato virus Y
A common potato virus that can cause severe yield loss
What is it?
PVY is a common, widespread potato virus that can decrease yield by up to 80%. Saving ‘seed’ potatoes from a virus-affected plant will lead to increased problems in the following year’s crop. The virus spreads easily, and potential losses are even greater when PVY is present with other viruses such as PVX.
What does it look like?
Symptoms are usually seen first in early summer. They vary according to the potato variety, the strain of PVY present and whether the virus originated in the seed tuber or from an aphid vector. Common symptoms include stunting, leaf mottling and crinkling. Sometimes older leaves shrivel up and remain hanging from the stem, a symptom known as ‘leaf drop streak’. Infected tubers may not show symptoms but occasionally light brown necrotic rings are visible on the skin.
How is it spread?
The virus is spread in growing crops by aphids. The mouthparts of the aphid quickly become contaminated when it feeds on a virus-infected plant. If it then moves to an unaffected plant and feeds it introduces the virus. The ability to transmit the virus is soon lost, but the aphid will become contaminated again if it feeds on another plant with the virus. Because the virus is picked up and lost by the aphid so quickly, it is not possible to prevent transmission by spraying the potato crop with an insecticide when aphid infestation is seen.
How can I control it?
A clean start to cropping can be obtained by using certified PVY-free seed, but this will not prevent subsequent aphid transmission of the virus to the crop. Regular monitoring for the virus and destruction of affected plants will help prevent rapid spread. Do not save seed if virus has been found in the crop.
When do I test?
Symptoms of PVY are likely to be first observed in June/July. Testing should be carried out as soon as symptoms are detected and monitoring for symptoms should continue until the haulm starts to die down.
What do I test?
Where possible, select areas of leaf that shows symptoms of disease. For best results do not use completely dead plant material. As a general guide, samples of leaf material should be approximately 25mm x 25mm.