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Source: Farmers Weekly [summ. Mod.DHA, edited]

Across Europe, a recent rise in seed potato crops being downgraded due to virus diseases sends a very strong message that a shift from individual control measures to a functioning, evidence-based integrated pest management (IPM) strategy is needed. Viruses that damage potato crops -- mostly spread by aphid vectors -- are not new, with widespread leaf "curl" documented in agricultural literature as early as the 1700s.

In Scotland, the Seed Potato Classification Scheme (SPCS) has strict virus tolerances in certified seed. The cool climate also helps produce high-grade stocks relatively free of disease that feed into seed multiplication and ware crops elsewhere. A range of highly effective insecticides to manage aphid virus vectors have also been available.

SPCS's data from the past 2 seasons shows a sharp upward trend in crops downgraded or failed due to virus. In 2022, 6% of crop area was downgraded and 0.3% failed because potato virus Y (PVY) and/or potato leaf roll virus (PLRV). By 2023, a significant jump to 15.4% downgraded and 1.8% failed was noted. PLRV was found in a majority of downgrade cases. Until recently, variants of PVY have been of greatest concern, but the persistently transmitted PLRV has made a rapid comeback. This shows the current trajectory and is a strong indication that action needs to be taken now.

Controlling viruses is a great challenge, particularly as winters become milder, aiding pest survival. Hotter summers then help aphids invade crops earlier when plants are most vulnerable, producing generations of young which build to damaging numbers much faster. In 2022, suction trap data showed the peach-potato aphid flying much earlier and in far greater numbers than the 35-year mean, leading to extreme vector pressure and the significant increase in downgrades and failures in 2023. Viruses can be transmitted incredibly fast, particularly non-persistent viruses such as PVY.

Managing strategies include preventing or avoiding sources of infection, such as volunteer or groundkeeper control, rogueing crops soon after emergence and throughout the season, as well as to remove groundkeepers from seed and surrounding crops. Proximity of seed crops to dumps of potato debris or poor-health ware crops is a significant risk factor.

[Byline: Richard Allison, Adam Clarke]

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[_Potato virus Y_ (PVY; type member of genus _Potyvirus_) is one of the most damaging potato viruses. Different strains of PVY can cause a range of symptoms, from a mild mosaic to severe foliar necrosis. The most virulent strain PVY-NTN causes interveinal mosaic on leaves and distinctive ringed necrotic areas on tubers. PVY can also affect tomato, capsicum and some other related species. It is transmitted by aphid vectors and can also be spread by mechanical means, plant-to-plant contact, or with infected planting material such as seed tubers.

The emergence of new and recombinant PVY strains is being reported from different areas (see previous ProMED posts in the archives). Numbers of co-infecting strains will build up with every crop cycle if PVY infected seed tubers are used, especially if these are moved to different areas where the virus strains they carry may combine with local PVY populations. PVY strains may also occur in (possibly synergistic) co-infection with others of the around 40 known potato viruses.

_Potato leafroll virus_ (PLRV; genus _Polerovirus_) is a serious pathogen of the crop and can be transmitted by aphids as well as seed tubers. PLRV can also affect tomato and a number of weeds; different potato cultivars may show different levels of susceptibility.

Since the crop is vegetatively propagated, many of its viruses may be disseminated in tubers. If virus-infected seed tubers are used, virus populations as well as numbers of co-infecting species and strains will build up with every crop cycle. This invariably leads to severely reduced plant vigour and a dramatic drop in yield. Disease management of potato viruses relies largely on clean planting material, but reduction of available virus reservoirs and vector numbers may also be useful. The important role that tubers play in virus and viroid spread is recognised by the strict requirements for certified seed potato production in many countries worldwide.

PVY symptoms on potato:,, and
Symptoms of different PVY strains:
PVY particles, electron micrograph:,_TEM.jpg
PLRV symptoms:, and

Additional news stories: challenges/, and
Information on _Potato virus Y_:, and
Review and diagnosis of PVY strains: and
PVY necrotic strains:, and
Information on _Potato leafroll virus_:,, and
Information on PVY and PLRV:
Virus elimination treatments:
Virus taxonomy via:
Information on _M. persicae_:
- Mod.DHA


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