Gardeners Advice For Potato Blight

Potato and tomato blight is a disease caused by the fungus-like organism Phytophthora infestans which spreads rapidly in the foliage of potatoes and tomatoes causing collapse and decay.

Potato blight – bin it, bag it, burn it

If you grow potatoes on an allotment, you could sign up to be a blight monitor, looking out for signs of the disease and sending in samples. This valuable work helps everyone who grows potatoes as the information is uploaded to web maps to show all confirmed outbreaks. This may give farmers time to protect their crops before they become infected.

The sample kits given out to the monitors are easy to use and postage is free. The work is not hard and won’t take up too much time. In addition, monitors receive a text confirmation of the presence or absence of blight from their samples, and updates during the growing season. 

If there is an outbreak in an allotment, it’s not just the potatoes close by that are at risk. Each blight lesion on a leaf or stem can release around 120,000 spores a day that can infect potatoes in other allotments and fields, so it is vital to keep a keen eye out for any signs of blight, and treat it accordingly. If you grow potatoes, bag, bin, and, where possible, burn any affected plants. The Potato Council has produced a fact sheet that explains in more detail what to look out for and how to control potato blight. Blight can also affect tomatoes, so you could lose your valuable tomatoes as well, if there is an outbreak.

Blight is more likely to occur during a ‘Smith period’, which is when the minimum temperature is 10ºC or above for two days, with a relative humidity of more than 90 per cent for at least 11 hours each day.  A 'near miss' can occur when conditions are not ideal for the spread of blight, but there can still be an infection risk for your crop.

Thanks to the work of monitors and scouts - commercial agronomists looking after fields -  everyone can keep up-to-date on Smith periods and the spread of blight by visiting www.potato.org.uk/blight and linking into Blightwatch, where you can register postal districts and receive warnings by email and/or text.

Potato blight is not a simple disease and it has many variations. Samples collected by blight monitors will be used alongside those collected by blight scouts to check for any changes in the kind of blight affecting this year’s crop. This helps lead to more in-depth understanding of new types of blight in Britain that can spread very quickly and are harder to control. Additionally, some of the newer types of blight infect crops at lower temperatures, so everyone needs to be vigilant.

It is thanks to the work done by blight monitors and scouts over the past few years that we have been able to discover, and get a better understanding of new types of blight infecting potatoes. If you would like to read more about potato blight, you can download the fact sheet below.

If you would like to become a blight monitor please email gary.collins@potato.ahdb.org.uk.  You will then receive a free sampling kit for this season.

Technical executive Gary Collins is Potato Council’s blight specialist