Many potato growers are still not testing land intensely enough for potato cyst nematode (PCN), warns John Keer from independent agronomy and analysis firm Richard Austin Agriculture.

Soil sampling is vital to identify PCN hotspots and develop an effective nematicide strategy, and the optimum testing intensity should be one sample per hectare, he says. “Most forward-thinking growers are already testing at this intensity, but there are still many in the industry only taking one sample per field or one sample per 4ha. That’s simply not enough and means you can easily underestimate or miss problems completely.”

Robust soil sampling is even worthwhile on land you may think is “clean” and free from PCN, he adds. “The overall cost of GPS sampling and PCN analysis is around £30/ha, which isn’t a lot on a crop that’s costing over £6,000/ha to grow, yet the impact of a PCN problem can be massive if you get it wrong.”

Hutchinsons root crop specialist Darryl Shailes says even low levels of PCN can have a significant impact on crop health, increasing susceptibility to key diseases such as alternaria and ultimately reducing yield and tuber quality.

He agrees that a testing intensity of one PCN test per hectare should be aimed for, with the soil sample taken from an aggregate soil sample made up of as many individual soil cores as practically possible. “The more soil samples you take, the better you’re chance of identifying any PCN hotspots. Ideally we aim for 50 soil cores per hectare.”

Mr Shailes says soil sampling and PCN testing forms just part of a long-term integrated plan for protecting land for future potato growing, alongside other factors such as variety choice, bio-fumigation, nematicide choice and crop rotation. “Controlling PCN is not just about the effects on the following crop. Good potato land is expensive to buy or rent and not easy to find, so we all have a responsibility to protect it as best we can for the future.”

Pressure on the existing armoury of nematicides also means it is vital that products are targeted as accurately as possible to keep on top of any potential threat, Dr Keer adds. “We’ve all got to ensure PCN levels are kept as low as possible to grow the crop sustainably in the future. We believe that PCN sampling once a hectare gives the optimum balance between time, cost and providing enough information to control PCN effectively.”