[Ian_A]

Ive got two lots of spuds to go - pink fir and cara - each still has lots of green foliage, they have also produced loads of those round poisonous fruit. But there is blight on the plots and there is some evidence of this on my potatoe leaves so I will cut down the leaves to ground level tomorrow- however,once I do this will the spuds below grow no larger?

[Trillium]

If the rest of the underground potato system is left intact, it will continue to grow for a short while more, but don't expect great growth. Mostly, the spuds will stay put in the soil, but if you think you've got blight starting, best to pull up the spuds, pick through for any damage, then place somewhere dark and coolish. You'll need to pick through another time or two to be sure blight isn't infecting the rest of the storage crop.

[someoneorother]

That is, when you cut down the foliage the potatoes will stop growing shortly thereafter. However, leave them in place for a couple of weeks to let any blight spores on the surface die off before you dig them up, to try and eliminate/reduce the risk of the tubers becoming infected.

At least, that's the advice I've always been given.

[mumofstig]

Here is John's advice

If you notice a small number of affected leaves with patches, you can try removing those and disposing of them. Burn if possible. This is a good time to make sure the potatoes are well earthed up to prevent spores getting into the tubers unless you have already done this. Spraying with Bordeaux mixture or fungicide may prevent spread if applied early enough.

If you have a more serious infection, then you need to cut off all the haulm and either compost or burn it. I think composting, especially hot heaps, will be safe but burning is 100%.

Removing the foliage prevents the disease getting into the tubers, as long as they are well covered with earth. Leave the crop alone for at least two weeks to let the blight spores on the surface die and the potatoes develop a thicker skin.

After harvest, check regularly for signs of blight and remove any suspect tubers at once from your store.