After I was informed that blight had arrived I drove to the garden centre to buy some Bordeaux mixture, only to discover that this traditional remedy has been taken out of service by European Union legislation. At this point I imagine the scurrilous anti-EU press trumpeting a headline,EU attacks our potatoes! They missed this one, but there was a reason behind the ban.Bordeaux mixture is composed of copper and slaked lime, but over the years in which it has been applied to soils on farms there has been an accumulation of copper in soils, leading to some toxicity. In excess copper does no good for soil life, such as worms. You can still purchase copper sulphate, but the garden centre had none in stock. However, knowing the need for copper to destroy the fungus I ordered some online when I returned home, express delivery. By the time that I am writing this sentence the copper sulphate has arrived, but the weather is wet and I will need a dry day to apply it. I am unconcerned about toxicity, for I have not overused copper as some farmers have, so my soil is not in danger of having too much of it.
But my neighbour, Ron, the gardening competition judge, had already acted. His potato crop is small and well tended, so he simply lopped off the tops of all the potatoes and dug them up. Doing this when you see the first sign of blight means that you kill the infected leaves before the fungus drops its spores into the soil. If you do this the potatoes are unaffected and are, though smaller than you hoped, perfectly edible. I checked a few of mine by digging them up, and found that they are small, the size of new potatoes, but are fine. I sought Ron's advice, and he suggested that as the infection was not present in all my crop,I monitor it and eliminate only infected plants.
Not all varieties are affected.First and second earlies rarely suffer, but main crop can get the disease badly. The Irish potato famine occurred because the Irish peasants grew a variety called the Lumper, which was a large, starchy,flavourless variety that sold well to the mass market of the English poor. The Lumper was very prone to blight, so Ireland took the full force of the disease. No one grows it now. Some varieties are bred for resistance, but the pathogen can mutate and so no one is really secure.
One important rule. When you rip up the infected plants, do not compost them on your garden compost heap. I took mine to the council tip [garbage disposal centre] and put them in the green waste section. The council works with a recycling company that has a hot composter, which is a tunnel into which the green waste is shoved. The heat inside is so great that break down of tissues is achieved more easily than the domestic compost heap can achieve, so the pathogen dies with the plant tissue,whereas in the domestic heap it can live on to infect more ground.