Potato Blight warning......

[isbister]

HDRA gives bordeaux mixture "Qualified Acceptance" whatever that is

[isbister]

[oubykh]

well its defiantly here in south wales, walked to my plot which is last down the path and many had already removed all foliage.

[artichoke]

I am glad I took a photo of my wonderful potato foliage three weeks ago before going abroad. Green, luxuriant, beautiful beyond description.

Went to see it today: totally vanished! All gone! Invisible! Disappeared!

Dug some lovely potatoes, though. Hundreds to come, if the slugs don't get them first.

[theothermarg]

i thought the best thing you could do is cut all the hullms(s?) off to the ground as the blight gets to the tubers through the leaves have done the 1sts will do the 2nds tomorrow
marg

[Kepouros]

Cutting off the haulm at ground level is indeed the final precaution, as the blight fungus does eventually travel down the stems to the tubers.  However, I have always regarded this as the final action when all other measures have been exhausted.  The blight fungus does not travel down the stems instantaneously, and how long it does take depends to some extent on the grower.

Removal of all infected foliage as soon as the signs of infection appear will reduce or delay the spread of infection through the plant, and repeat spraying will reduce the chances of remaining healthy foliage being affected.  These two measures combined can allow the grower ( and the plant) a further two or three weeks for immature tubers to develop before the plant has to be cut down - and that point is generally reached when approximately 80% of the foliage has been affected.

Certainly, first early potatoes will, by now, have had their day, and there is nothing to be lost by cutting them down immediately, but the tubers of many second earlies are still at an immature stage, and most of the maincrops have not yet even started tuber initiation.  For these crops an extra two or three weeks can make all the difference between little or no crop and some crop or a crop worth having.

However, a word of warning (which I have made before on other similar threads). When you cut down the haulm DO NOT rush to dig up the potatoes immediately unless you intend to use them quickly.  If the haulm has got blight then the soil surface below it will most certainly be covered with live blight spores, and bringing the tubers to the surface will simply allow those spores to get onto the (still soft) skins of the tubers, which will then rot in storage.
Leave the tubers underground for a full two weeks to allow the spores to die and the skins of the tubers to set.