Diseases of Potatoes: Viral and Viral-Like

Calico Mosaic
Alfalfa Mosaic Virus (Calico)

What to look for?

Photo: Howard

Picture description Mottled leaves are sometimes seen in potato fields as a consequence of virus infection.

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Management strategy
Infection is aphid-borne from alfalfa and few plants are usually affect.


Corky Ring Spot
Tobacco Rattle Virus (TRV)

What to look for?
This disease is rare in Canada but much more common in the US.

Photo: Howard

Picture description Tuber necrosis is a consequence of infection.

Photo: Howard

Picture description Malformed tubers as a consequence of TRV, drought, herbicide residues or Rhizoctonia solani infection have similar symptoms.

Management strategy
None

Leaf Roll
Potato Leaf Roll Virus

What to look for?
This virus is particularly destructive to Russet Burbanks.

Photo: Evans

Picture description Net necrosis of the tubers in storage. Tubers are unusable for chipping due to this virus infection.

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Management strategy
Use virus-free certified seed. Seed potato plots are top-killed and harvested early primarily to avoid late season infection of this virus from Viriliferous aphids.

Rugose Mosaic
Potato Virus Y and/or Virus X

What to look for?
The "N" or necrotic strain of PVY caused considerable seed grower losses in Eastern Canada. The "N" strain causes problems in tobacco.

Photo: Evans

Picture description Wrinkled leaf with severe effect on growth.

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Management strategy
Potatoes are no longer grown near tobacco crops but infection of potatoes by the N strain is for a non-tariff barrier to seed potato export.

Spindle Tuber
Potato Spindle Tuber Virus

What to look for?
This virus disease is very rare in Canada since it has no vector and transmits very poorly or not at all when in contact with other tubers.

Photo: Evans

Picture description Infected tubers; Russet Burbank, spindle shaped.

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Management strategy
Another example of a disease that had its infection consequences much overblown.

Witches' Broom
Witches' Broom Mycoplasma (Aster Yellows Phtoplasma) and Clorerphyllody

What to look for?
These are mycoplasma or mycoplasma-like organisms (MLO) that are virus-like in some ways and vectored by leafhoppers. In the Pacific Northwest, infection levels may be as high as 5% in harvested tubers.

Photo: Evans

Picture description Upright multi-branched plant. Dozens of small shoots from one potato eye.

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.Management strategy
These diseases are self-eliminating since they do not spread from potato to potato.

More information about bacterial diseases of potatoes can be found at Pest Management - Diseases - Viral. This is part of the Guide to Commercial Potato Production on the Canadian Prairies.

Photographs and information assembled and prepared for ARD by Dr. Ieaun R. Evans Agri-Trend Agrology Ltd.