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.
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Fungal infection can affect experts. Monty Don, an expert gardener who presents the television programme Gardener's World, someone whose advice I value, lost his box hedges to box blight.All he could do was rip them up and replace them with other species.
Sadly, the blight got into the greenhouse. The speed at which it arrived was unsettling.One day, just a few symptoms, next day, despite spraying,it was all on one side. I sprayed again and thinned out unproductive stems to allow air in. My aim is to preserve the tomatoes. We might be in line for some decent weather in the next day or two, which might help.
Gardening, as with other things, requires knowledge. You are ahead of many by knowing what is happening and taking act.
I saw a few smitten leaves in the greenhouse, but this time I had the time to act, so today I gave the whole set of plants a good spraying with copper sulphate. But greenhouse work was all that I could do today, as the weather is very wet.
The disease dwells in living tissue and dies quickly outside it, but potatoes are often left in the ground after picking, as some are missed by the picker, so the pathogen can linger in the tubers, if it has got into the soil. I think a year will be enough if the disease is caught and treated early, but otherwise two years or more might be necessary, as it will take that amount of time to guarantee that scutch potatoes that are acting as pathogen reservoir are destroyed.
I read an article today by Charles Dowding, an expert, who thinks that the pathogen will die in a garden compost heap, as the living tissue in which it is embedded is decomposed, but I am not totally convinced, so I prefer hot composting just to make sure.
How long does it take for the disease to be gone from the soil altogether? Is a year's wait long enough?
Well,I am going to grow potatoes in containers with fresh soil, though I am placing them on the opposite side of the garden to the infected area. Butt in the area which has been most badly it, which is one bed in particular, I may grow make a three sisters bed, which is maize, pumpkin and beans grown as companion plants.
I had tomato blight a few years ago and lost my lovely crop. What will you plant in the infected garden area next year?
I think that next year I will grow the tomatoes in my new greenhouse, which is further away from the blight afflicted area than my first greenhouse is. I will use greenhouse number one for plants that are not susceptible to blight, maybe using it primarily for bringing on seedlings. Playing safe,really.
However,what did I just say about digging up the potatoes? The weather here is very wet, it has not stopped raining all day, so there is little gardening being done.
Today I am finishing the job of clearing the affected bed, then I am digging up the potatoes, as they won;t grow after the plants are gone. But they will still be healthy and edible.