Tomato blight and potato blight

Posted: Wednesday 11 June 2014
by Pippa Greenwood

How can it have happened so early? That was my first thought when I read the panicky texts and emails from a fellow panellist on GQT.

How can it have happened so early? That was my first thought when I read the panicky texts and emails from a fellow panellist on GQT.

The cause of the panic? Phytophthora infestans, more commonly known as potato blight and tomato blight - the miserable fungus that's most notorious for the Irish Famine or 'Great Hunger' of the 1840s.  

Usually, I experience blight in my garden in the month of July, and sometimes even in August. Never before do I remember it being so widespread this early in the year. The mere mention of blight in the first half of June has turned me into a nervous mother hen, clucking over the haulms of my potatoes. What I'm checking for are those first tell-tale symptoms, namely black blotches on the stems or foliage. So far, so good. I urge any of you who are growing potatoes or outdoor tomatoes minus any cover to check your crop daily, if possible. A preventative copper fungicide spray is also recommended.

The blight fungus soon causes haulms to flop as discolouration spreads and, when the weather's particularly moist, humid or wet, slightly fluffy white fungal patches may develop beneath the leaves and on the discoloured patches on the stems.

Once blight has struck, there's little that can be done. The spores that develop on the haulms are easily washed down into the soil by rain or overhead irrigation. Once in the soil, the fungus may then attack the potato tubers, thereby decimating the crop.

If you spot the symptoms I've described, the best course of action is to cut off all the infected or suspect areas immediately, in a bid to stop the spores reaching the tubers. This impedes the ability of the tubers to swell - but better to have fewer, smaller potatoes than none that are edible. Bin, burn but don’t compost all you remove... and good luck to you in the battle of the blight.

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Talkback: Tomato blight and potato blight
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happymarion 19/06/2014 at 09:09

The "Charlotte" potatoes I an trialling for Mr. Fothergill are harvested from the potato planter bag and being eaten. very delicious and a good crop. Such a clean way to grow potatoes. The same weight of tubers is being grown in one of my raised beds for comparison so I am keeping a sharp eye on them. the flowers have been removed so the harvest should be pretty soon. I think they will win cropwise but of course I have to dig them out instead of tumbling them out on to a sheet of plastic. We, the Nation of Gardeners Team are trialling 6 kinds of tomatoes, one blight resistant one so it is a worrying time, but I have put mine in the lea of the house which has saved my crop in former blight ridden years by sheltering them from the rain containing the spores and from the windblown ones as well.

Welshonion 19/06/2014 at 10:06

There is early blight and late blight.  You may not get blight at all.  We grow earlies to avoid it. And tomatoes in the greenhouse for the same reason.

Why have you removed the flowers from the potatoes?  There is no need.  If there are any flowers they can give a rough guide as to whether it is worth digging a plant.

Jill Stephens 06/09/2014 at 18:57

My tomato crop was ruined by blight this year. I understand I can't plant tomatoes or potatoes in the same plot for 3-4 years! How far away do I need to plant next years plants- 1 metre- 3 metres or 10 metres away? Also is it OK to plant any other crop in place of the former? Would a bonfire on the spot kill the fungus, or is there some other way to clean up the plot?