About a week ago, when the weather was hot and humid and rainy, I noticed some yellow leaves on the spuds. And some green leaves with the tell-tale black circles on. Blight!!
Of my 6 varieties I am growing this year, the earlies (Accord) were just about finished. The second earlies (Vivaldi) and salad potatoes (Charlotte) were going yellow very quickly. However, one maincrop (Sarpo Mira) was completely untouched, and two (Kifli & Cara) were only slightly affected.
My neighbours immediately cut down all their potato haulms and encouraged me to do the same.
It's a tough one. The maincrops are only just now flowering, so the potatoes under the ground will still be quite small. If I cut them down, they won't grow any more anyway.
So this is what I did. I cut down the Accord, Vivaldi and Charlotte. I didn't buy these for their blight resistance, although traditionally Charlotte is meant to have good resistance to tuber blight, if not on the leaves.
I will leave these under the ground for a full 3 weeks. By which time any fungal spores in the ground are meant to be inactive and the tubers safe to lift without infecting them.
The bed of Cara have a few yellowing leaves, which I have carefully picked off. Traditionally Cara has had strong blight resistance, hence their nickname "The Allotmenteer's Friend". However in recent years new strains of blight have taken up residence in the UK. The latest, called I think Blue 13, is really nasty and I suspect a lot of our potato-resistance databases are out of date nowadays. So whether my Cara survive or not without me chopping them down waits to be seen.
Kifli and Sarpo Mira are 2 varieties from the Sarvasi family. The story goes that in the Soviet era, this family were told to develop blight-resistant potatoes. When the Soviet Union broke up, they came to the west with some of their most resistant spuds hidden in suitcases.
They have continued their breeding programme here, and I buy their varieties (through Thpmpson & Morgan). Sarpo Mira is not the tastiest of spuds, and can be rather strangely shaped, but if everything else dies, at least these should survive. Kifli is a more recent variety - I have read conflicting accounts of its resistance - so now we will find out. Incidentally. for a maincrop, Kifli tastes superb, just like new potatoes.
So I have been picking off the leaves from the Cara and Kifli and hoping for the best.
Now that the humidity has gone and the temperature is high, (Summer has finally arrived!!) I am hoping that the disease will become inactive.
Incidentally, there is conflicting advice as to what to do with the haulms. Most old sources say they should be burned. But some more recent authorities suggest they can be put on the compost heap. I have decided to compost them, though if I have any infected tubers, I will dispose of them elsewhere. I don't use that compost on the spud beds anyway.
The tomatoes in the greenhouse have been largely unaffected. (The blight-resistant varieties of tomato are far less resilient!) I did find the early stages of blight on a couple of leaves, which I carefully picked off. After that I kept the greenhouse door closed until the temperature soared a couple of days ago. When going into the greenhouse I made sure that I did that business before doing anything else on the allotment, to reduce the risk of bringing blight in.
I think I might have have got away with it!
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