Blight on the landscape

By February 27, 2018Articles

Val Bourne looks forward to a bumper organic potato crop – if the blight stays away

lifting potatoes anya harlequinfor web

‘Anya’ and ‘Harlequin’ potatoes that survived the attack of blight

As an organic gardener I like to grow my own food and, as I once had a lowly post at the National Vegetable Research Station in Wellesbourne, Warwick, I feel that I’m keeping my hand in. We have vegetable plots in the garden and an allotment within walking distance.

We grow all our own potatoes because commercial crops are sprayed with fungicide every seven days in order to prevent potato blight. That’s an average of 16 times from planting to harvest. Crops are also sprayed with weak acid to kill the top growth, and then the tubers are usually sprayed with anti-sprout to stop them chitting and greening up under supermarket lights.

The maincrop varieties we grow are ‘Cara’, ‘Harlequin’ and ‘Victoria’, and we grow them on the allotment. ‘Cara’ used to be blight resistant, but it’s now susceptible because strains of potato blight mutate. The classic symptoms are yellowing on the foliage and black lesions followed by collapse of the foliage.

NP Wikimedia-Late_blight-Phytophthora_ for web

Classic blight symptoms are black lesions followed by a collapse of foliage. Wikimedia Commons © Howard F. Schwartz, Colorado State University, United States

 

This fungal disease, caused by Phytophthora infestans, is spread by spores travelling in the wind and mild, damp Augusts encourage it. Cutting off the stems can limit the damage to the tubers, but the haulms should be put in a green bin, not on the compost heap.

Certain varieties are more resistant than others and for many years ‘Cara’ shrugged it off. There are also completely blight-resistant varieties, such as ‘Sarpo Mira’, but I don’t find them very palatable.

One wet year we escaped potato blight completely, much to our surprise. We relinquished our tidy allotment plot and took on another much weedier one. It rained a lot and soon our potato crop was completely covered in weeds – so much so that it was impossible to see our potatoes at all.

August came and everybody’s potatoes were hit by blight. We lifted ours in September, with little expectation, but with virgin ground and plenty of rain, our potato crop was abundant. One variety
was ‘Harlequin’, which has fairly good blight resistance. Check your varieties out at varieties.ahdb.org.uk/varieties.

 

Top Tip

When choosing potatoes, go for flavour. ‘Harlequin’ (below) is a tasty, high-yielding waxy potato, and I enjoy eating ‘Roseval’, a red French main crop that’s delicious baked because the flesh is very creamy.

Potato 'Harlequin' MIW252243

© Alamy

 

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