PCN testing could give potato growers greater control

That was the message from PCN Action Scotland at James Hutton Institute’s Potatoes in Practice event, where Kerry Leslie of SAC Consulting and James Price, project lead, presented findings from the project, which came to an end this year.

And for Leslie, the starting point is simple: test the field before the potatoes go in.

“Before planting any potatoes, we would love every field that is going to have potatoes in it to be tested for PCN, whether that is statutory testing through SASA or commercial testing of ware crops,” she said.

The reason is clear. PCN can cause yield losses of up to 80% when populations are high, with Scotland facing both Globodera pallida and Globodera rostochiensis .

Price described it as a problem growers inherit rather than one that simply disappears between crops.

“You cannot sleep on PCN. If it has been in the field, it is probably going to be there for a while, and it needs to be at the forefront of your management strategies,” he said.

The project has also highlighted the growing role of resistant varieties, with Price describing resistance as the industry’s strongest tool during the growing season.

“Resistance works. It works incredibly well. It is our best tool in the growing season to manage PCN,” he said.

But one of the most interesting discussions at Potatoes in Practice centred on where and when growers should test.

A question from the floor asked whether soil collected beneath the grader could be tested for PCN, potentially giving growers an indication of which fields were carrying the pest.

Leslie agreed it could provide useful information – but warned that unless soil movements could be traced back to individual fields, it would be difficult to pinpoint the source.

That prompted one grower to point out that boxes are already tracked by field, while another suggested marking boxes could allow contaminated areas to be identified.

Price acknowledged the possibility, but said the timing of testing remained important.

Testing before planting gives PCN populations time to naturally decline during the rotation and allows growers to make management decisions before committing to a crop.

“If you want to identify the absolute highest-risk fields and simply see whether anything is there, then testing under the grader makes sense,” he said.

For Leslie, however, the ultimate goal would be much more precise sampling.

Rather than the traditional W-shaped field sample, she suggested a grid-block approach which could create a map showing exactly where PCN was concentrated.

“It would allow you to tackle it much more precisely, rather than simply knowing there is PCN somewhere within a large sample block,” she said.

The technology and knowledge may be developing, but the message from the project was straightforward: PCN management starts with knowing what is beneath growers’ feet.