How to avoid potato blight

I can’t remember a worse year for growing potatoes than 2012 – spring droughts, late frosts, low temperatures and high rainfall resulted in poor growth, high levels of disease and disappointingly low yields. But while we can’t do much about the weather except pray to the sun gods, there are many ways in which gardeners can minimi se the risk of blight damage this summer. It’s all a question of “knowing thy enemy”.

Potato blight

Potato blight, or phytophthora infestans , is a genetically complex, highly adaptable fungus that can wreak great damage on unprotected potato crops, as evidenced by the Famine of the 1840s. The bad news for gardeners is that blight researchers have discovered that new, more aggressive strains of the disease continue to evolve.

Traditionally, blight has been controlled by the regular use of a preventative fungicide such as Dithane or copper-based sprays, but a growing band of gardeners are choosing to avoid the use of such chemicals. Capitalising on the fact that different potato varieties vary greatly in terms of their resistance to the disease, they’re instead switching to those with good blight resistance such as the Sárpo range. Developed by the Sarvari Research Trust in Wales, these spuds are the result of a decades-long breeding programme begun by the Sárvári family in Hungary.

The Sárpo “family” includes Sárpo Mira and Sárpo Axona (both main crop, red-skinned and floury), Sárpo Una and Kifli (earlier and waxy), Sárpo Shona (white-skinned) and Blue Danube (blue-flowering and blue-skinned). They’re available as seed potatoes from a variety of stockists including Mr Middleton (mrmiddleton.com) and the Secret Garden Centre in Cork
(the secretgardener.com).

A handful of other maincrop varieties also showing excellent blight resistance include Bionica (early main crop and floury), available from Fruithill Farm (fruithillfarm.com). Dermot Carey, the market gardener who tends Harry’s Bar and Restaurant’s walled kitchen garden in Donegal, also highly recommends Tibet, another dark-skinned maincrop variety only available as a seed potato to members of the Irish Seed Savers’ Association.

For information on the Sustainable Potatoes United Development Study (Spuds) campaign to encourage Irish gardeners to grow blight-resistant varieties of potatoes , check out spuds.ie.

Blight-resistant varieties aside, there are a number of other important ways in which gardeners can protect their potato crops. First, always source good-quality, certified seed-potatoes from a reliable supplier and plant as early as possible.

Second , concentrate on early varieties, which have a far shorter growing season (roughly 14 weeks) than main crop potato varieties ( 18-20 weeks), making them less vulnerable to attack. Third , always practi se good garden hygiene. Be mindful of crop rotation – the longer the cycle, the less chance of passing on disease. Old potato “dumps” on the ground from last summer as well as any “volunteers” left in the soil to re sprout can act as a source of re-infection, so remove these by burning or bagging them. Plant at extra generous spacings, to discourage blight . Watch out for signs of disease (dark-brown patches surrounded by a pale “halo”, visible on wilting foliage and stems) and pay attention to blight warnings. If blight hits, cut stems back to ground level and dispos e of them .