Protecting our humble spud

Authors: Ian Toth and Damian Bienkowski (James Hutton Institute)

Potatoes - Image by Skeeze (Pixabay)

You have probably heard of the Irish and Scottish potato famine of the 1840s, where the food supply of millions was devastated by the disease ‘late blight’, caused by the plant pathogen Phytophthora infestans. Late blight is still a problem for potato growers, but nowadays it is kept largely kept at bay with fungicides and with disease-resistant potato varieties. But the humble spud is far from safe - there are over 100 other pests and diseases that threaten UK potato production, some of which, like late blight are already here, but with many more threatening our boarders. You may not know that in there are two kinds of potato sold in general, one is the kind you eat (in their many delicious forms) and the other is the kind you plant, called seed potatoes. Seed potatoes must be produced to a very high plant health standard, so that they don’t carry pests and diseases. Scotland produces approximately 75% of all seed potatoes grown in the UK, underpinning a domestic potato sector valued at £167 million and providing the foundations for GB production, which has a retail value estimated at over £4 billion - certainly not small potatoes! According to the industry, one out of every four British potatoes ends life as a chip, with around 300 million portions being sold annually.  Chips tend to get a bad rap when it comes to health concerns, getting lumped in with ‘junk food’, but they are actually one of the lowest calorie takeaways, with a third of your daily vitamin C requirements and double the fibre of a serving of brown rice or porridge.

One of Scotland’s strengths in potato production is the relative freedom from pests and diseases compared to more southerly nations, which is largely due to our cooler climate. This is clearly a great advantage for Scotland, but one that can be easily undermined if we let our guard drop and allow the pests and diseases gain a foothold.

Perhaps the biggest new threat to potato is from the disarmingly named ‘Zebra chip disease’. But don’t let visions of herds of potatoes on the Serengeti distract you! Zebra chip is a dark striping in the potato when cooked (hence the name), which are bitter, making the crop unsellable. Potato production in the USA and New Zealand has been devastated by this disease, and the culprit is a bacterium (Liberibacter). Like many plant diseases this pathogen can’t move between plants alone, it need to be transmitted by a vector – in this case by sap-sucking flies called psyllids. While we don’t have the Liberibacter pathogen in Scotland, we do have the psyllids, meaning that if it ever arrived here it could migrate though our crops, so vigilance is critical in keeping the pathogen out. Because of our high health seed potato status, Scotland imports very few seed potatoes, helping to stop Liberibacter and other pests and pathogens crossing our boarders. However, the growing increase in trade of all commodities means that they could one day find their way to us through other routes.

It is important there to keep a close watch on new threats and on those pests and pathogens that are already here. Industry, government and scientists in Scotland are working closely together to ensure that we remain one of the best seed producing and exporting nations worldwide. As part of this partnership we continue to find new ways to manage plant health. For example, the Scottish government-funded Plant Health Centre helps to raise awareness of plant pests and diseases specifically in Scotland, and to assist government, farmers, foresters, nurseries and those working in the natural environment in provide information that will help to manage their plant health needs.  It is important therefore to have clear and simple messages that apply to all those with an interest in maintaining plant health and this includes the public. We have therefore developed a set of five ‘Key Principles’ to minimise plant health risks in Scotland. While the Key Principles are primarily a tool aimed at professional growers and traders of potatoes (and all other plants) to help them assess their ‘biosecurity’ practices, there are a few steps that anyone can take to help keep our potato industry safe from threats:

When buying seed potatoes for your garden it is always better to buy local, as the further the potatoes travel the more chance of pests and diseases they bring. Do they have a ‘plant passport’ or other plant health credentials? Don’t be afraid to ask your supplier if this isn’t clearly stated. Have you found a cheap source on the internet which doesn’t give plant health information and you don’t know where this seed has come from? If the answer is yes then it’s not worth the risk.  Have you found some seed tubers while travelling but don’t know their plant health status? Again, consider plant health. It’s not worth the risk and this of course applies to all plants and not just seed potatoes.

Another important step you can take is to properly dispose of any diseased plants. Remember that basic hygiene plays a huge part in maintaining plant heath so, like other pathogens in the news lately, wash your hands and equipment, especially after handling diseased materials and dispose of it carefully – remember a pile of rotting plant material in your garden could be the start of a new disease outbreak for the whole nation.

Hopefully by reading this article you will have gained a wider appreciation of the importance of plant health, not just for potatoes but for all plants. Find out more about the Key Principles and plant health in general by visiting www.planthealthcentre/key-principles, and please pass on information to others.

Right I’m off for some chips!