SCOTTISH POTATO growers have been warned that there might not be a seed industry in Scotland in 30 years’ time if the spread of potato cyst nematode (PCN) continues at its current rate.

As growers gathered to attend the UK’s largest potato conference, Potatoes in Practice – at the James Hutton Institute’s Balruddery Farm, in Invergowrie – there was a sense of urgency for the industry to unite in its approach to tackling PCN, to ensure the long term survival of the sector.

It has been revealed that 5% of seed ground in Scotland is now infested with the potato pest and with a longevity of 25-30 years – that means that land can be rendered commercially useless for spuds during some of that time.

The director of Scotland’s Plant Health Centre, Professor Ian Toth, warned that using globodera resistant varieties of potatoes is having little to no effect against the pallida species.

“In Scotland, SASA (Science and Advice for Scottish Agriculture) regularly tests seed ground and found that around 5% of land was infested with PCN. Something like 33% of untested ware land we believe also has PCN.

“There are several different ways to control PCN, with cultivar resistance being the main one and about 50% of potato land in Scotland uses globodera resistant varieties,” he continued. “However, the problem is, there are very few varieties which are resistant to pallida, which means probably 90% of all cultivars that we plant in Scotland are susceptible to the species.”

He explained that pallida is becoming a growing problem with the amount of land infested by the species doubling every six or seven years. “If we keep going at this rate, within the next 25-30 years there might be no land left to plant potato seed. Urgent action is needed now, because if we don’t move for the next five years, we will have twice as much pallida as we do now.

“There needs to be a coordinated approach by the entire potato industry bringing together growers, agronomists, researchers, processors and customers to ensure an integrated approach to tackle this.”

Mr Toth stressed that one of the first steps to be taken was to ensure more growers were aware of the potato pest – following a recent survey by SASA which found that over 40% of growers were unaware if the varieties they were using were resistant to PCN.

The Plant Health Centre has commissioned work to pull together a list of resistant varieties to the different globoderas and to look at recent breeding programmes, to see where the industry is at, in terms of resistance for cultivars in Scotland.

“Upcoming talks with the Scottish Government will focus on funds from science research programmes such as the James Hutton Institute, to see if we can speed up the identification of markers that show resistance to pallida using various techniques,” Mr Toth continued. “We also want to look at modern breeding technology to see whether we can speed up the deployment of those markers into varieties we are going to breed in the future.”

Adding fuel to the fire, the potato industry has lost an important herbicide and desiccant – diquat – which has been used by growers in the UK for more than 50 years to desiccate foliage on the potato plant.

Chemistry loss also took centre stage at the conference and it was revealed that there are further chemicals expected to end up on the hit list for being taken out of the grower’s armoury, though discussions focused around alternatives to replace diquat.

Greg Dawson, of Scottish Agronomy, discussed current trials looking at alternative haulm-destruction methods for high-grade seed crops: “The loss of diquat is a real problem for the industry, for all varieties, but particularly for those indeterminate varieties with vigorous canopies. We need new products or methods that promote rapid haulm kill to reduce the potential for disease developing in store.

“Currently, there are no chemical treatments which are as effective as diquat at killing off the mature leaf,. Potential alternatives, such as Gozai (pyraflufen-ethyl) and Spotlight Plus (carfentrazone-ethyl), are mainly used for stem destruction,” he added.

AHDB’s senior knowledge exchange manager, Claire Hodge, explained that trials are being carried out on five farms UK-wide, working with growers to find solutions: “Our strategic farms are ideally placed to help growers find alternatives as they can trial different practices in a commercial environment and make sure the results are swiftly shared with growers.”

She explained that chemical and mechanical methods are being tested which will also identify the most cost-effective approach for growers in the future. Mechanical possibilities suggested included flailing and root under cutting which involves cutting the roots below tuber level, which she explained could prove difficult in Scottish stony soils and the increasingly wet weather.

“We have a big list of products which we are looking at, but not just focusing on chemistry,” Ms Hodge continued. “We are trying to work with more organic farms to make sure we look at techniques used on the other side as this has to be a whole integrated approach.”

SRUC’s Dr Andy Evans called on the industry to take check of their biosecurity measures on farm and how they could look at stemming the spread of PCN via machinery.

“Everyone in the seed industry needs to focus on the fact PCN is on the rise and we need to look at our own farm biosecurity as PCN spreads on machinery. If someone has a PCN infested field, there will be machinery going into that field, not just for potatoes, but for other crops and therefore could be trundling PCN all over the place,” he warned.

Mr Evans urged growers to be wary of using contractors and to look at how they can stem the spread of PCN between farms, making the point that the sector needs to get up to speed, fast, on ways to reduce the spread of the disease.