http://www.thegrocer.co.uk/fmcg/fresh/fruit-and-veg/allotment-amateurs-are-making-potato-blight-worse/233373.article#comments_form
Telling gardeners to buy well-produced potatoes from their retailer rather than growing their own is not a good idea - it will fall on deaf ears. Why do gardeners bother to grow their own? Exactly because they do not want to buy "well produced potatoes" sprayed every week with chemical fungicide.
There are several issues involved here and in some of the press articles propagated by that article. This is how I see it:
Blight has been rampant in gardens and allotments this year - this bit is certainly true.
Amateur growers have less effective control available - meaning chemical sprays - true - heavy metal poison copper is the only approved blight spray and who wants to use that? The farmer has many, (mostly less toxic) sprays he/she can buy. Thus most amateurs do not spray and, in a year like this, their crop gets totally blighted and spores drift off to infect healthy potatoes in the vicinity. Should this be a concern for farmers? Hmmmm! If their crops are regularly doused in chemical does it matter that much? The problem is that continuous wet weather prevents the spray tackle getting on the field every 4 or 5 days to keep that protection intact. So chemical control is less than 100% and spores from gardens could do some damage.
Blighted foliage should not be put on the compost heap - Hmmmmm! It would be better to put it on the heap AND cover it up rather than leave blighted foliage lying around to keep generating spores. There is no convincing evidence that the blight pathogen survives more than a few weeks in a compost heap or in the soil as the spores need to infect potato tissue if they are to survive. (where both mating types of the pathogen are present in a crop there is a very low probability that resistant oospores form and contaminate the compost and infect a new crop the following year). Hygiene is important so cutting off foliage and composting it reduces transmission to other crops.
'Gardeners do not know how blight should be controlled' (and don't care). Fact sheets and websites on blight and its control are readily available already and mean that the amateur is now much better informed about control. There is certainly more scope for spreading good practice more widely e.g. all waste and undersized tubers should be destroyed - in a tank of water or buried DEEPLY. Tubers should NOT be kept for seed as some may be blighted and these can produce blighted plants in the new crop. Buying in certified seed every year is always worth while.
But the elephant in the room is that the industry and amateurs are growing varieties that are susceptible or highly susceptible to blight. If all varieties grown were resistant or even moderately resistant, control would be much easier. An increasing number of amateurs already grow resistant potatoes like our Sarpo varieties and their popularity is increasing. They have been the only crops able to survive in many gardens this year. Of course amateurs also grow very susceptible "heritage" varieties. Professionals do not grow resistant varieties - why would they do that as you can make a variety resistant if you keep it sprayed and even some of the newest varieties grown for the supermarkets are VERY susceptible. Since amateurs rarely spray against blight, growing resistant varieties would certainly cut down the transmission of spores from allotments into farmer's fields.
Potato Industy - put your house in order: start growing resistant varieties, stop polluting our planet and stop blaming gardeners!
 |
| An early infection on a local allotment this year that is destoying a crop soon after it emerged. Soon there will be nothing left. Best to remove and compost the foliage to destroy the spores. |
