Six steps to managing the virus burden in potatoes

The high health status of Scotland’s seed potatoes is a matter of industry pride and vital to the marketability of seed stocks.

But aphid vectored viruses in potatoes are increasing year on year so following the Six Steps to effective virus management is vital.

These are thrashed out by experts across the Scottish industry as part of the Scottish Aphid Borne Virus Working Group and give the consensus view on best practice each year.

Step 1: Isolate crops from sources of infection

Sources of infection include infected seed planted in a field, other potato crops, potato volunteers, and uncontrolled growth in potato dumps so place crops away from these sources and use as healthy seed as possible. You know likely sources of virus for your own ground but not necessarily for neighbours so good communication between growers is a good first step.

Step 2: Remove virus infected plants wherever they occur

Rogue early and remove infected material before virus can spread because if infected material can be removed before aphid vectors are present in significant numbers, the transmission cycle can be broken.

Quick disposal of rogued plants is also important as they will still serve as a virus source if left in piles at crop edges.

Step 3: Use resistant varieties, mitigate risks in high propensity varieties.

Potato varieties vary a great deal in their resistance to different viruses so pay particular attention to those known to be weak, and isolate away from other crops where possible. Some varieties are known to have high “virus propensity“ UK potato varieties database are a good source of information and ratings provide a useful guide, however the complexity of viral strains means that, practically for PVY, they cannot wholly be relied upon.

Step 4: Act on monitoring information

Get traps out early and look at suction trap and yellow water trap (YWT) data regularly so that you can use it to inform spray programmes and other control measures.

Met data is helpful in giving a general indication of likely aphid activity, but the most reliable indicator is direct trapping and YWTs provide the best source of locally relevant information. Albert Bartlett are funding the YWT scheme in Scotland this season, as they did in 2023.

Step 5: Use targeted spray programmes

This needs careful planning as you are managing two issues with insecticide spray programmes – non-persistently transmitted viruses (potato virus Y) and persistently transmitted viruses (potato leaf roll virus), and there are resistance issues in some actives such as the pyrethroids.

Mineral oils, approved as adjuvants, have an effective contribution to play in PVY control. They can sometimes add to the risk of scorch especially when applied in warm and sunny weather conditions, so a bit of planning is required (i.e. what time of day sprays applied).

Step 6: Continue control measures until haulm is dead

Spray programmes need to be kept going until all green plant material has died, and it is important to prevent and control any regrowth too.

Timely haulm destruction is also an important control measure.

The Six Steps document will be updated for 2024 (by a consortium that includes SASA, JHI, SPO, BPTA, PBGA, McCain, Agrovista, Scottish Agronomy and SRUC) on the SASA website – the 2023 document link is here. The six steps remain the same, but the new document will be easier for growers to put into action. Expect to hear more details very soon.

There’s innovative work going on in the area of aphid vectored virus control, including using camouflage systems early in the season to confuse aphids and prevent them finding host potato plants.