Symptoms caused by Potato Virus Y (PVY) vary quite extensively in appearance and also severity, from negligible to severe. This is due to the strain (type) of PVY causing the infection and the potato variety. PVYNTN is now the dominant of the 3 PVY strains occurring in the USA. Its presence has resulted in this disease re-emerging to become a serious problem in the USA. This is partly because PVY is difficult to detect in many varieties because of very mild symptoms. Consequently PVY is difficult to detect in seed potato fields. This was not the case before 1990 when the ordinary strain (PVYO) occurred.
Following images are of potato variety ‘Nadine’ which developed severe foliar symptoms at two farms on Long Island in 2016. Necrotic veins, especially visible on the underside of leaves (images on right), is a characteristic symptom. Symptoms became widespread likely due to aphids being present to move virus among plants; another possible explanation is high percentage of seed containing the virus. PVYNTN was confirmed using molecular techniques.
Left: upper leaf surfaces. Right: lower leaf surfaces. Click images for larger view.
Below, field where above leaves were obtained. (Photo: S. R. Menasha, Vegetable/Potato Specialist, Cornell Cooperative Extension – Suffolk County)
Following images are of mild symptoms commonly caused by PVYNTN in several potato varieties. Affected plants are stunted with leaves that look crinkly and are thicker than those on healthy plants.
PVYNTN reduces potato yield because affected plants produce fewer and smaller tubers, and the tubers have necrotic rings. Severity of symptoms varies among varieties. Below, potato tubers with necrotic ringspot caused by PVYNTN. (Third photo courtesy: Dr. Steve Johnson, University of Maine Cooperative Extension. Fourth and last: Sandra R. Menasha, Vegetable/Potato Specialist, Cornell Cooperative Extension – Suffolk County)
Potato Virus Y is managed by:
- Selecting resistant varieties.
- Planting only certified seed known to have little or preferably no detectable PVY based on post-harvest virus test. Tolerance is < 5%.
- Disinfesting all equipment used for cutting and planting between seed lots. PVY can be mechanically transmitted.
- Destroying cull piles that could serve as a source of PVY and rogueing volunteer potatoes.
- Limiting transmission of virus by aphids. Most insecticides that control aphids are of limited benefit for managing PVY because many aphids are able to pick up and also to transmit this virus very quickly, faster than an insecticide can act (non-persistent transmission which takes seconds). Insecticides that may be beneficial:
Mineral oils, such as JMS Stylet Oil and Aphoil, that interfere with non-persistent transmission by removing the virus from the aphid’s stylet as it feeds.
Anti-feedant compounds or selective feeding blockers, such as Fulfill or Beleaf, applied when aphids are known to be entering potato fields.
For more information see: Managing Potato Virus Y in Seed Potato Production