The recent warm temperatures and high humidity have been ideal for the spread of potato blight, a fungus-like organism that spreads rapidly in the foliage and tubers of potatoes and tomatoes.
It is quite likely that we may already be seeing outbreaks of the disease on our crops and if identified, action should be taken immediately to prevent the disease reaching the potato tubers.
You may notice brown freckles on the leaves or sections of leaves with brown patches and a sort of yellowish border spreading from the brown patch.
In a severe attack you may discover that all the foliage is down and brown, starting to rot. It’s frightening how quickly potato blight can spread in the right circumstances.
If you identify blight on your potatoes, cut off the haulm and bin or burn it. Do not put infected material in your compost bin.
Your potato tubers won’t develop any further if you cut the tops off, but leave them in the ground for 3 weeks nonetheless. This will help stop the blight spores getting onto the tubers as you harvest them.
After harvesting and storing, check potatoes regularly for signs of rot and remove any suspect tubers at once from your store.
For more information about potato blight go to Allotment Gardens or the RHS