Potato blight is very destructive and can wipe out a full crop overnight. In a sack or a crate, it will travel from potato to potato, ruining them all. Potato blight is one of the worst diseases you can get while growing potatoes and the
moist, humid Irish summer climate is perfect for spreading it.
Causes of Potato Blight:
Potato blight is caused by a fungus called Phytophthora infestans, which can spread to other members of the potato family, including tomatoes. It spreads through the air and develops when the weather conditions are warm and humid, particularly during a Smith Period. A Smith Period is a 48 hour period in which the minimum temperature is 10°C or more and the relative humidity exceeds 90% for at least 11 hours during the first 24 hours and at least 11 hours again during the final 24 hours. However, any period of warm, humid weather increases blight risk.
Symptoms of Potato Blight:
Brown freckles of patches on the leaves
Yellowish border spreading from the brown patches
Dark patches on tubers
Inside of the tuber is brown and rotting from the skin down
The potatoes will eventually turn into soggy, foul-smelling masses.
Treatment of Potato Blight:
If you notice a small number of affected leaves with patches, you can try removing those and dispose of them.
This is a good time to make sure the potatoes are well earthed up to prevent spores getting into the tubers, unless you have already done this.
Spray with blight control spray as this may prevent spread if applied early enough.
If you have a more serious infection, then you need to cut off all the foliage and stems and either compost or burn it.
Removing the foliage prevents the disease getting into the tubers, as long as they are well covered with earth.
Leave the crop alone for at least two weeks to let the blight spores on the surface die and the potatoes develop a thicker skin.
After harvest, check regularly for signs of blight and remove any suspect tubers at once from your store.
Prevention of Potato Blight:
The best way to prevent Potato Blight is to plant a good blight-resistant variety. The best product on the market for the prevention and control of blight, is Proxanil.
Blight Resistant Varieties:
The recent development of Sarpo Hungarian varieties is a real breakthrough in potato cropping. They are extremely blight resistant and are available from Horkans. Sarpo Mira is a wonderful variety that is floury, well flavoured and a terrific cropper. It is a nice red skinned potato with lovely white flesh. Other blight resistant varieties include Orla, Colleen, Golden Wonder, Kerr’s Pink and Record.
Please remember to follow instructions carefully when using chemicals.