Kitchen Garden - Potato Blight
The December issue of Kitchen Garden has a lot to say about blight and offers a rebuttal of the "gardeners to blame for blight". Lots of good advice on control and use of varieties with blight resistance. Thanks KG
Bingo! We done it
We are delighted to announce that our crowd has got us to our target with time to spare. We now have a great crowd of supporters that is still growing. You may have noticed we have a second milestone to get the project to £10000. Our first target of 5k gets us part way to progressing our new variety but the 10k total should get us all the way. Many, many thanks to our 55 backers for their support and generosity. We hope you will enjoy participating in the project.
Allotment amateurs blamed for blighting UK potato crop?
Have you seen the furore sparked off by a bit in The Grocer about interviews with The Potato Council?
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!
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. |
Have you joined the crowd?
We are delighted that the crowd is growing and we are almost half way to our target of £5000.
Join the crowd now and get regular updates of our progress (or lack of) in the next few months. Do remember that there is just him and me running the show so sometimes, eg when one of us is away, you may have to be patient if you are waiting on a reply to a question.
It is really easy to join up so why not do it now. Our crowd now has several prominent supporters that I know you would love to meet and talk potatoes to. You will get that chance early next year at our Potato Day - date to be arranged.
Just go to our page on the buzzbnk website
Join the crowd now and get regular updates of our progress (or lack of) in the next few months. Do remember that there is just him and me running the show so sometimes, eg when one of us is away, you may have to be patient if you are waiting on a reply to a question.
It is really easy to join up so why not do it now. Our crowd now has several prominent supporters that I know you would love to meet and talk potatoes to. You will get that chance early next year at our Potato Day - date to be arranged.
Just go to our page on the buzzbnk website
Join our New Crowdfund Project
Why not participate in getting a new, blight resistant potato developed? You can become a Cheerleader and tell your contacts about the project or you can contribute as little as £10 to help us get the project started. Those contributing more money can get their hands dirty growing this new Crow (short for Crowdfunded) spud or test some of them in the kitchen and send us your results. We will have a Potato Day for the Crowd sometime in March when you can visit us at Henfaes Research Centre and hear all about our progress and plans. We aim to raise £5000 over 100 days. Please help us.
Potato Blight on Gardeners Question Time this week
If plot had bad blight this year, can the soil be cleaned of blight and how soon can I plant potatoes again?
Answer was: Spores wash into soil. Wait 3 years before replanting. Always bin or burn diseased foliage.
Hmm....
Actually, spores quickly die off in soil unless they infect a new potato tuber. You could plant potatoes in the same plot the following year and you would not get blight. However, if any tubers left in soil at harvest get infected then the blight can (low probability) survive and grow into the volunteer plant the following year. Replanting will encourage any potato cyst nematodes in the soil and certain other diseases will be promoted so it is always better to rotate.
No need to bin/burn blighted foliage for same reason. The pathogen needs a living host to survive and will not survive in the compost heap or even in foliage left to rot on the soil surface.
There are very very rare exceptions to the above that need not worry the grower.
Answer was: Spores wash into soil. Wait 3 years before replanting. Always bin or burn diseased foliage.
Hmm....
Actually, spores quickly die off in soil unless they infect a new potato tuber. You could plant potatoes in the same plot the following year and you would not get blight. However, if any tubers left in soil at harvest get infected then the blight can (low probability) survive and grow into the volunteer plant the following year. Replanting will encourage any potato cyst nematodes in the soil and certain other diseases will be promoted so it is always better to rotate.
No need to bin/burn blighted foliage for same reason. The pathogen needs a living host to survive and will not survive in the compost heap or even in foliage left to rot on the soil surface.
There are very very rare exceptions to the above that need not worry the grower.
Saving Blighted Tomatoes
In a bad late-blight year, tomatoes often get infected just as the first fruits ripen. All you can do is pull the plants up and save all ripe and mature green fruit that look healthy. These tomatoes can be spread out in a warm, dry spot to ripen fully. But this is often a waste of time as it is very likely that fruit are already infected and that they will rot before they ripen. Don't despair! We have worked out a simple method to cure infected fruit, that is, to kill off the blight pathogen without damaging the tomato. See The Organic Grower, 11, Winter/Spring 2010, p31: No more green tomato chutney: how to cure blighted tomato fruit.
Essentially, green fruit with latent blight infection was incubated at 40C for at least 12h, then ripened at room temperature. Control fruit rotted before ripening but blight was eliminated from the treated fruit. Small quantities of fruit are easily treated in a chicken-egg incubator and some domestic ovens can be set to hold 40C (104F). An alternative is to use a water bath (fish tank?) and put fruit in polythene bags.
Higher temperatures for shorter times might be effective but tomato fruit might suffer some damage.
Essentially, green fruit with latent blight infection was incubated at 40C for at least 12h, then ripened at room temperature. Control fruit rotted before ripening but blight was eliminated from the treated fruit. Small quantities of fruit are easily treated in a chicken-egg incubator and some domestic ovens can be set to hold 40C (104F). An alternative is to use a water bath (fish tank?) and put fruit in polythene bags.
Higher temperatures for shorter times might be effective but tomato fruit might suffer some damage.