Late Blight

[jayb Enjoying the scenery. Find all posts View Profile Close jayb]

First sign of Late Blight, an almost unnoticeable mark and easy to walk past.
I picked the leaf and placed it between a layer of damp kitchen paper which I placed inside a plastic bag and left it overnight. It was clear it was indeed Late Blight in the morning, but then again so were several other leaves in the potato patch! Not sure if it helps but at least if it were something else such as Early Blight you could rule Late Blight out.

[Galina Isolating and Pollinating Find all posts View Profile Close Galina]

Hmm - isn't one of the characteristics of late blight that the spots extend to a leaf edge as a rule? None of your spots in the picture above go to the edge, although I agree, the colour looks exactly like late blight.

Disposing of plants that are affected by late blight is the worst job in the garden every year. Quite depressing, especially when it happens early.

[jayb Enjoying the scenery. Find all posts View Profile Close jayb]

The pictures show Late Blight in it's earliest stage, I think if it can be spotted at the earliest point you have some chance of giving the crop a little extra time to set tubers or let them bulk out a little if it strikes early it their cycle. By removing the affected leaf/leaves and surrounding foliage it can give that little bit of extra time to the remainder of the crop, though much is dependant on the weather conditions at the time and daily removal of any further signs. The first picture shows just as Late Blight first shows on the surface of the leaf, no signs on the underside. The second two are approx 10-12 hours later and I had kept this sample longer the spread would have been rapid over the leaf. Late Blight spots are often seen on or near leaf edges or the tip of a leaf as this is where water drops can collect.

Yes cutting down, otherwise healthy and robust plants in their prime is horrid. I think every year I say I'm not growing them again.