Potato Viruses Y and A (PVY and PVA) is the second most important potato virus. It is perpetuated through infected tubers and transmitted by aphids in a nonpersistent manner. Potatoes yield losses may reach 80%.

Symptoms of Potato Viruses Y and A

Symptoms of Potato Viruses Y and A vary widely with virus strain,Potatoes  cultivar, and environmental conditions.
Rugosity, bunching, twisting of leaves, downward turning of leaflet margins, stunting, necrosis of leaflet veins, necrotic spotting, leaf necrosis, and stem streak are typical.
Less sensitive potatoes cultivars may react by developing with only a mild mosaic, or they may be infected symptomlessly.
PVA is in many respects similar to PVY.
When present in certain cultivars, it is generally less severe than PVY.
Potatoes yield losses may reach 40%.
PVA causes mosaic (sometimes severe), as well as rugosity and crinkling, and leaves may appear shiny.
PVA symptoms are usually milder, but cannot be easily distinguished from those of PVY.

Management

Management of PVY and PVA is by clonal selection and roguing in seed propagation. Resistant potatoes cultivars are available.

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Symptoms of disease caused by Potato Leafroll Virus

Primary symptoms caused by currentseason aphid-transmitted infection are rolling of upper potato plants leaves, especially of leaflet bases. These leaves tend to be upright and are generally pale yellow.
With many cultivars, they are tinged purple, pink, or red. Late infections may not cause symptoms, whereas some cultivars are infected symptomlessly.

Potato tubers of highly sensitive cultivars develop net necrosis in the flesh. Secondary symptoms (of plants grown from infected tubers of subspecies tuberosum) are rolling of basal leaves, stunting, upright growth, and paleness of upper leaves.

Rolled leaves are stiff and leathery, and sometimes tinged purple on their undersides.

Subspecies andigena reacts differently: it develops marginal and interveinal chlorosis, especially of upper leaves, marked upright growth, and often severe stunting.

Rolling of lower leaves is usually lacking. Natural transmission is by aphids in a persistent manner, and through infected tubers.

Management

Potato Leafroll Virus can be managing by selecting healthy plants gor growing and eliminating diseased plants through roguing in seed propagation.

Systemic insecticides will decrease spread by aphids within the crop but will not prevent infection by viruliferous aphids from other fields.
Potato Leafroll Virus is the only potato virus known to be eliminated from tubers by heat treatment.

Resistant potatoes cultivars have been developed recently.

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