The conditions this year have been perfect for potato blight
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Go Organic: Beware potato blight
By James AshfordJuly 13, 2012
Potato blight is one of those things you have to get used to as an organic gardener.
In fact even conventional gardeners don't have anything in the chemical cupboard to control it effectively.
The surprise this year is not that we have blight appearing down at the allotment but that it has taken so long to get to us.
The conditions this year have been perfect for potato blight.
Wet day and warm nights allow the fungus to spread and take hold and it is starting to appear on plots across our site.
For purely practical reasons potato blight can be divided into two different varieties.
What we are getting now is the less-serious early blight, Alternaria solani. It is unsightly and annoying but it doesn’t have to spell disaster.
Blight appears as dark brown or black patches on the leaves sometimes surrounded by a pale halo. It spreads quickly to the rest of the plant and to its neighbours.
When you see blight, cut out the affected parts of the plant immediately and dispose of them in the black wheelie bin.
In the unlikely event of the weather turning dry you may be able to stop the blight spreading.
If the crop is more seriously infected and the disease has appeared on more than 10 per cent of your plants more drastic action is needed.
Cut off all the foliage and dispose of it in a hot compost heap or in your black bin. This will stop your spuds getting any bigger – but it will mean that the crop that is already underground will be saved.
Wait for three weeks before lifting the crop. With the foliage gone the blight spores will die on the surface of the soil and the tubers should be saved.
Late season blight, Phytophthora infestans, is a much more serious affair. It was what caused the Irish potato famine and because it gets into the tubers it will cause them to rot in storage.
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