A group of 42 growers, farmers, and industry representatives from across Scotland has met to take action against the threat of potato cyst nematode (PCN) to Scotland’s potato industry.
Held in Angus, the area of the UK worst affected by PCN, this was the first meeting of a new Soil Association Scotland-led Rural Innovation Support Service (RISS) group formed to unite the industry against a pest that could wipe out Scotland’s potato industry in 25 years.
Facilitated by Calum Johnston of SAC Consulting, part of Scotland’s Rural College (SRUC), the meeting saw speakers from SAC Consulting, SRUC and SASA outline the available data on the spread of PCN and potential control methods, followed by group discussions on viable options to halt the spread of infested land.
Speaker Jon Pickup of SASA said: “We’re seeing an exponential increase in our findings of pallida in Angus alone. At the moment we’re finding PCN in about 500 hectares per annum, but the exponential spread means that by 2025 this could be at 1,400-1,500 hectares. With 6-year rotations, the management decisions we make now will only change things from 2026 onwards."
The pallida species of PCN is a particular concern, with the amount of infected land doubling every six or seven years and it may take up to 30 years before infestations decline to allow seed potatoes to be grown on that land again. The financial implication of this is concerning. Pickup added: “Estimates are that we’re at a loss of £2-3 million per year in seed potatoes and a built-in £5-6 million loss by 2025.”
Picture: A packed room to discuss the threat of PCN in Cupar Angus on Nov 5 2019
A long-term solution discussed was the need to grow varieties of potato resistant to PCN. But of the top 15 major Scottish varieties of seed potatoes currently grown, only Innovator and Royal varieties are resistant to pallida, and issues with demand exacerbate this problem. Kim Davie, also of SASA, said: “Most pallida- resistant varieties are processing varieties, but in Scotland our ware market is for table varieties. There are only a few pallida resistant varieties currently suitable for use as table varieties and the question is how do we get supermarkets to take these resistant varieties. It’s getting people wanting to buy them and getting companies wanting to sell them.”
Dr Andy Evans of SRUC also outlined some options for controlling PCN in the shorter term, although this can be difficult within Scotland’s climate. Dr Evans explained that the best way to start is with soil sampling: “The best approach really is to know what you’ve got. Sample fields to get an idea of the PCN species and population.”
“If you’ve got high egg counts, you really do need to think about a long rotation of 10 to 13 years, grow resistant cultivars, and consider biofumigation or trap cropping. If you’ve had a low PCN count and grown a resistant variety, it’s still worth resampling after the potato harvest to see where you are. It’s better to take a sample immediately after a potato crop.”
The meeting concluded with a roundup of the initial ideas that came out of group discussions. Stuart Wale of SAC Consulting summarised these: “We have some excellent information on how a small change in resistance makes a big difference to the build-up of PCN. Resistant varieties are the long-term solution, but we’re not there yet, so we need to encourage breeders.
“In the short term, growers are going to have to look at other control measures. We’ve heard that biological options like trap cropping, biofumigation and plant extracts are difficult in Scotland, but with no other alternative, we need guidance for growers on how to do this.
“One clear takeaway from today is that we really ought to be doing more testing, both pre-planting and post-harvest. It means spending more money, but we then know what we’re individually facing. There’s also a responsibility from testing organisations to look at the cost of testing.”
Following on from this first meeting, the Rural Innovation Support Service (RISS) facilitator Calum Johnston will form a steering group of growers and industry representatives to take the ideas from the first session forward.
A second RISS group, facilitated by SAOS, has also recently formed to research whether a compost high in chitin, made using the waste shells from Scottish shellfish, can act as a non-chemical method of decreasing the level of PCN in potato and daffodil bulb fields.