Scientific Name
Potato Virus Y (PVY)

Identification
Symptom expression depends on the potato variety and the virus strain. Shepody is very susceptible to PVY, although the symptoms may disappear in a few days. In Russet Norkotah the symptoms are not noticeable (latent infection)

• Crinkled and curled leaves with yellowish or light green colored mottling. Mottles are variable in size and are not delineated by leaf veins.
• Often, the infected leaves develop necrotic spots.
• Plants are stunted, lower petioles and leaves turn yellow, and dead leaves cling to the stem. This symptom is called leaf drop. PVY-infected plants usually die early.
• Infected plants produce fewer and smaller tubers than healthy plants.
• Darkening of veins caused by PVY infection. This symptom is called vein banding.

Often Confused With
Other potato viruses

PVY Strains
Lately, new strains of PVY have developed. These strains cause less severe foliar symptoms but some cause necrotic symptoms in tubers.

PVY^N
These strains cause a necrotic reaction on tobacco leaves but not on potatoes. They cause milder symptoms on potatoes than those caused by PVY⁰

PVY^NTN
This strain is a PVY^N type that causes necrotic flecking and ringspot symptoms in the tubers of some potato varieties

PVYN:O
These strains are thought to have some characteristics of both PVY⁰ and PVY^N

Period of Activity
Plants from infected tubers show PVY⁰ symptoms within 2-3 weeks after emergence. Current season infection develops after aphids probe and or feed on potato plants.

Scouting Notes

• Scouting should start shortly after crop emergence.
• Fields should be scouted at least twice a week to rogue infected plants and to monitor aphids.
• When walking fields, stop at many sites as possible and check plants at random.

Thresholds
Many aphid species can transmit PVY⁰.  Monitoring and controlling aphids should reduce the incidence of this disease.

Advanced

Scientific Name
Potato Virus Y (PVY)

Identification
Symptom expression depends on the potato variety and the virus strain. Shepody is very susceptible to PVY, although the symptoms may disappear in a few days. In Russet Norkotah the symptoms are not noticeable (latent infection)

• Crinkled and curled leaves with yellowish or light green colored mottling. Mottles are variable in size and are not delineated by leaf veins.
• Often, the infected leaves develop necrotic spots.
• Plants are stunted, lower petioles and leaves turn yellow, and dead leaves cling to the stem. This symptom is called leaf drop. PVY-infected plants usually die early.
• Infected plants produce fewer and smaller tubers than healthy plants.
• Darkening of veins caused by PVY infection. This symptom is called vein banding.

Often Confused With
Other potato viruses

Biology
PVY⁰ is the common strain of the Potato Virus Y complex and is the most important virus infecting potatoes in Ontario. PVY⁰ persists in infected seed potatoes, volunteer potato plants and cull pile tubers. PVY⁰ is introduced into a potato field either by planting infected seed tubers, by aphid transmission during the current season and by mechanical transmission. Plants from infected tubers show PVY⁰ symptoms within 2-3 weeks after emergence. Current season infection develops after aphids probe and or feed on potato plants.

The hairy nightshade weed is susceptible to PVY⁰ and may be an important source of the virus late in the season. Ground cherry and dandelion are also hosts of PVY⁰. Other crops attacked by this virus are tobacco, tomatoes and peppers.

The virus is transmitted by aphids in a non-persistent manner. The green peach aphid is an efficient vector of PVY. Some mechanical transmission of PVY can also occur. Other aphids that do not colonize potatoes transmit PVY to the crop when probing plants. The bird cherry-oat aphid is also an important vector of PVY.

PVY Strains
Lately, new strains of PVY have developed. These strains cause less severe foliar symptoms but some cause necrotic symptoms in tubers.

PVY^N
These strains cause a necrotic reaction on tobacco leaves but not on potatoes. They cause milder symptoms on potatoes than those caused by PVY⁰

PVY^NTN
This strain is a PVY^N type that causes necrotic flecking and ringspot symptoms in the tubers of some potato varieties

PVYN:O
These strains are thought to have some characteristics of both PVY⁰ and PVY^N

Period of Activity
Plants from infected tubers show PVY⁰ symptoms within 2-3 weeks after emergence. Current season infection develops after aphids probe and or feed on potato plants.

Scouting Notes

• Scouting should start shortly after crop emergence.
• Fields should be scouted at least twice a week to rogue infected plants and to monitor aphids.
• When walking fields, stop at many sites as possible and check plants at random.

Thresholds
Many aphid species can transmit PVY⁰.  Monitoring and controlling aphids should reduce the incidence of this disease.

Management Notes

• Use certified seed potatoes with the lowest virus level allowed by the seed certification program.
• Control volunteer potato plants, weed hosts and eliminate cull piles to reduce inoculum sources.
• Rogue and destroy PVY⁰ infected plants including tubers in seed fields.
• Time insecticide applications to control aphids. This should reduce PVY⁰ spread.