Topic: Blight - The WHICH trial report.

[tim]

Thanks to their free trial, & Ross's steer, I now have it on file.
Nothing tremendously exciting but, as with most reports, worth a browse. It sets out to find tactics for survival after blight has struck. Resistant varieties, spraying & protecting from rain seem to be the main saviours. Had they had the torrential rain of this year, the results might have been very different.
Because of the rain, I'm afraid that, despite cutting out the haulms, the spores will have been washed deep down into my best maincrop ever - Picasso - with tubers up to 2lb. = Tim

[Hugh_Jones]

tim, I`ve never considered merely removing the haulm as being a sufficient protection when blight strikes.  However carefully this is done there are almost invariably small pieces of foliage and stem detritus left which can harbour the spores, and unlike the spores on the soil surface these will probably survive the 3 week wait.

The solution (which I have suggested often enough on both the BBC and these boards) is to cauterise the potato bed with a flame gun as soon as the haulm is removed.  Done competently this will sanitise both the soil surface, and any debris left on it, so there is nothing left to wash down into the soil  It also has the benefit that the crop can be lifted as soon as one wishes instead of leaving it to the tender mercies of the slugs and wireworm for 3 weeks

[tim]

Hugh - forgive me if I've asked this elsewhere, but can't find it.
Given that I was unable to flame, & given that the rain has been torrential since blight struck, and since the haulms were cut 2 weeks ago, might it not be sensible to lift the pots now & reduce slug risk? One would assume that, whatever I do, the spores will be happily infecting the tubers by now?? = Tim

[Hugh_Jones]

Tim, I do not regard the 3 week `safe period` recommendation as being cast in stone.  Plants where the haulm is removed early require a longer period for the tubers to set their skins - this is the 3 week period.  However, plants from which the haulm is removed later require a shorter period to set the skins, and 14 days should be quite adequate.  Indeed, where the haulm has been cut late it is advisable to lift the crop after 14 days simply to prevent tuber infection from spore percolation through the soil. The answer, of course, is to lift one and test the skins for firmness, and, if they are set, to start harvesting.

However, here are two sites which I have referred to frequently in the past and which you may find helpful to refer to for future use. Both are somewhat lengthy, but well worth reading through:-

http://www1.sac.ac.uk/info/External/About/publicns/TN/TN491.pdf

and
http://www.ruralni.gov.uk/pdfs/publications/orgpotat.pdf

[tim]

 Thanks. Hugh.  I'll be back in a week after digesting that? Hadn't thought about the skins maturing. They are baking so thinly crisp as they are now. = Tim