Potato blight can devastate a promising crop of spuds in a matter of days. It’s frustrating, exasperating and dispiriting! But take a few precautions and you can avoid this fungal disease altogether, says Benedict Vanheems

Benedict Vanheems

Blight is more than just bothersome – it’s downright infuriating! We’ve all been there: you’ve patiently chitted your seed potatoes, dutifully planted them on a fine April morning, then nurtured them to full leafy splendour… only for the foliage to collapse, seemingly overnight.

Potato blight has a long history of ravaging our favourite vegetable. In Ireland a series of crop failures caused by blight led to the Great Famine of the 1840s, when an estimated one million people died and a further million emigrated. Perhaps the reason behind its ruthless efficiency is the ease with which the spores of this fungal disease spread – carried on the wind from field to field.

There’s no mistaking those tell-tale first signs of blight. Small dark spots or lesions appear on the leaves, often with a fine, white, powdery growth around the edges. Serious infestations will spread to engulf the foliage, causing stems to collapse and leaves to look almost burnt. Infected tubers will develop brown or purple patches that become brown and grainy as the disease spreads towards the centre.

THE SCIENCE BIT

To plan defensive measures against potato blight, it’s necessary to understand the enemy. Both potato blight and tomato blight are caused by the same fungus, Phytophthora infestans.The disease spreads quickly in warm, humid weather.This usually means the first signs of blight are spotted in the second half of summer, though infection can begin from June in southern counties.