Potato Virus Y

Potato virus Y (PVY) is the Big Daddy of potato problems, right up there with early blight. And potatoes aren’t the only plants at risk. Peppers, tomatoes, and groundcherries can all catch PVY. Losses can be as high as 80%. Infected potatoes that make it to harvest don’t last in storage. And who wants to eat an infected potato?

Potato infected with necrotic ringspot (Chrisvis1) CC BY 3.0

Potato virus Y is spread by aphids, but not in their saliva. Instead, these microscopic potyviruses stick to aphids’ mouthparts (stylets). As the vector aphids feed, they spread the disease. Your shoes, clothes, and garden tools can also transfer this virus.

Tobacco leaf infected with PVY (R.J. Reynolds Tobacco Company Slide Set, Bugwood.org) CC BY 3.0

The many flavors of PVY

PVY used to be easy to identify. This meant infected plants were removed right away, and the spread of disease was limited. Like another virus that shall remain unnamed, the PVY virus has been mutating a lot lately, making it more difficult to manage. Recent mutations have fewer symptoms, making infected plants harder to identify. They stay in place longer, increasing the spread of disease to nearby plants.

Tobacco leaf showing mild PVY symptoms (R.J. Reynolds Tobacco Company, Bugwood.org) CC BY 3.0

The most common variations of PVY include PVYO (ordinary), PVYC (uncommon)­, PVYN (necrotic), PVYNTN (tuber necrosis), and PVYN-Wi (a recombinant strain). The tuber necrosis strain can cause potato tuber necrotic ringspot disease (PTNRD). Botanists sure do like their acronyms, don’t they?


Potato virus Y symptoms

Brown spots on leaves and tubers are the first sign of potato virus Y infection. Other symptoms vary depending on the plant age and health at the time of infection, environmental conditions, potato cultivar, soil health, virus strain, and the presence of other viral diseases, such as PVA, PVS, and PVX. Chlorosis, curved midribs, leaf crinkling, mosaic, mottling, and vein distortions are early signs of PVY. Infected leaves feel rough (rugose) compared to healthy leaves. If you look on the underside of infected leaves, you will see dark lesions and black streaks on the midrib. As the disease progresses, leaf loss and stunting are common. This disease is easily mistaken for calico (alfalfa mosaic virus).

Tomato leaves infected with potato virus Y (Scot Nelson) Public Domain

Potato virus Y management

Chemical treatments are not effective against potato virus Y, so these good cultural practices are your best line of defense:

• Start with certified pest- and disease-free seeds and seedlings.
• Choose a resistant cultivar well-suited to your microclimate. [Belrus, Dark Red Norland, Eva, HiLite Russet, Kennebec, Monona, Norwis, and Sebago are all resistant varieties.]
• Space plants in such a way that minimizes exposed soil, or use reflective mulch. [The color difference between plant and soil has been shown to attract aphids.]
• Plant as early in the season as possible.
• Super light horticultural oils may be used to manage aphids. [Farmers also use systemic insecticides.]
• Remove and destroy infected plants.
• Start each growing season with new seed potatoes.