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Trouble in the potatoes

Posted by Guy Barter on 30 Jul 2007 at 10:02 AM

More rain, more blight and more spraying.  Unfortunately the spraying has not held up the blight and most spuds have been cut back as not being worth continuing with.  Clearly, I did not spray as often and as thoroughly as I could have done, although under current weather conditions I would have been lucky to be blight free. 

This is not as bad as it seems as the majority of the affected spuds are second earlies that are either finished or coming to an end anyway or ‘Euro' cultivars of spuds that are so ill-adapted to a maritime climate that they are expected to perish from blight at the first opportunity.  Few Continental potato cultivars are grown for this reason, although I cannot resist trying. 

However, I am disappointed that ‘Robinta' recommended for a broad, if modest level, of blight tolerance should succumb so readily.  It is an early maincrop so much of its yield potential has been achieved.  My other significant maincrop ‘Ambo' is holding its own (with the help of Dithane).  This is of Irish origin so I expect it's partial resistance is better than the Dutch ‘Robinta'.  The blight resistant Sarpo cultivars are disease free. 

Second earlies, include Cosmos which is typical of the heavy yielding modern ones. These are nearly as heavy cropping as maincrops but easier to grow being out of the ground in good time to avoid slugs, the worst of the blight and leaving the soil free for autumn crops.  It also have a good flavour. 

The other important second early is Charlotte, a potato of excellent flavour.  Her Loveliness has let it be known that this is the one she expects to be served from now on. This year it has cropped very well with many large tubers.  Last year, like most of my potatoes, it ran out of water and just died leaving a light crop of scabby, small tubers.  I considered dropping it for 2007, but in this moist season it is an excellent performer. 

As the foliage was cut a gloved handful of soil was placed over any exposed tubers.  A gloved hand and my ‘harvesting knife' were used for the cutting back.  This knife is an old stainless steel serrated carving knife kept hidden on the plot for harvesting jobs - severing courgettes, pumpkins, cabbages and cauliflowers is short work with this knife.  

A black plastic sheet was then spread over the potato plot to prevent weeds and exclude rain until harvesting time.  At least two weeks will be needed by the tubers to form a robust skin that will allow them to be stored and indeed for the infectivity of blight spores on the soil surface to decline.  

At least I won't have to apply two tankfuls of fungicide every few days. 

The plastic sheet had been covering ground that had carried a crop of peas and that had become thick with weeds as often happens in pea crops.  The weeds having been killed by the sheet, were raked up and French beans and courgette plants were set out.  While I was at it I filled in gaps in the beans sown earlier this month. With rain forecast there was no need to water them in. 

The diseased haulms will be composted.  Blight spores are not long lived and should not survive in the compost.  However, I will be sure not to use it for potato ground next year.  There is a resting spore that could resist composting, but my information is that this is seldom encountered in Britain.


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