Symptoms on foliage

Symptoms caused by PVA vary widely according to the combination of the virus strain, the potato cultivar, the environmental conditions and the type of infection, either primary or secondary infection. 

In the case of an infection occurring during the current year, the infection may be symptomless or the symptoms may take the form of slight, transient mosaic symptoms which can be seen mainly in overcast weather. Mosaic patterns are alternating patches of light green and dark green areas without any leaf distortion and PVA discolourations/mottles are often not limited by veins. This symptom pattern can be more visible by placing a sheet of white paper under the leaf concerned. 

In the case of an infection that occurred the previous year, the symptoms may be far more pronounced, possibly with wrinkling of the leaves accompanied by symptoms of brightness (photo 1) and more or less severe mosaic symptoms depending on the cultivars concerned (photos 2 to 5).

Potatoes infected with PVA in combination with PVX or PVY may show pronounced symptoms such as crinkling, severe leaf deformation and yield reduction.

Symptoms of PVA are more easily observed in cold and cloudy weather.