Onion White Rot -- Again!!!

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Johnboy
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Hi Realfood,
Thank you for that thread and I am going to have to think hard how the application can benefit the gardener in the absence of a wheat crop. Just off the top of my head Grazing Rye springs to mind but would that be there long enough? Could you grow Grazing Rye on to fruition? If it is going to benefit you in the long run then it may be something similar to this train of thought.
Thinking caps needed!
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Johnboy, I would be very interested to know what role grain plays in the cycle and the application of the onion or garlic for onion rot, I seem to be missing the connection but I am sure you have good reasons for including it.
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Johnboy
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Hi NB,
Had you read the Farmers Guardian thread posted by Realfood you would have come across this passage.

“The compost needs to be applied at least six months, ideally longer, before seed drilling or set planning to maximise the germination of sclerotia and avoid phytotoxicity to the onion crop. Applying the compost before an intervening wheat crop, which benefits from onion waste compost, is the best treatment,” said Dr Noble.


I was wondering about the Wheat part as it is not really part of a gardeners remit and what could be used instead of it. I thought Grazing Rye as the nearest thing to wheat. It was a gambit to try and spread this thread because to me it is an extremely beneficial weapon in a gardeners armoury if it can be made to work garden-wise.
JB.
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Tony Hague
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I would be fairly certain that Ralph Noble's advice on the wheat crop is not to do with any active effect of the wheat, it is simply a matter of timing. You need to add the composted onion waste, then wait for six months. A grower is not likely to want to leave a field covered with nice compost to grow weeds. The timing is right to follow onions with winter wheat, and the wheat benefits from the compost.

Remember that we are talking commercial agricultural "rotations" here, where effectively monoculture with a break crop one year in ten is not uncommon !

This is probably one that is easier for the amateur gardener, just using the onion preparaton before any non-allium crop would probably do.
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Dear Johnboy,
sweetcorn perhaps?
Regards Sally Wright.
Nature's Babe
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Thank you Johnboy, sorry, i overlooked that. :oops:
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DiG
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The responses to my 'bit of bother' has generated some very interesting reading. Thanks folks. Time for some experiments I think. Nothing ventured nothing gained.

Diane
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Johnboy
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Hi Tony,
May I respectfully ask you to read the Farmers Guardian Thread again, as what I read is that it needs a break crop to feed on the composted onion prior to replanting an allium crop.
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Tony Hague
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Ok, let me quote the relevant bit of the article

“The compost needs to be applied at least six months, ideally longer, before seed drilling or set planning to maximise the germination of sclerotia and avoid phytotoxicity to the onion crop. Applying the compost before an intervening wheat crop, which benefits from onion waste compost, is the best treatment,” said Dr Noble.

So, he says that you need to apply it at least six months before you sow/plant an onion crop (to allow the onion volatiles to do their job, and the white rot to die), and that it is best to apply before a wheat break crop (which will provide a break of > 6 months), so that the onion compost benefits the wheat. Read again - the onion compost benefits the wheat as a side effect, not the wheat crop benefits the process.

So, I go back to what I said - on a garden scale probably any crop which is not an allium will do to provide a season's break before replanting onions. Good choices could be anything that would benefit from the additonal compost. I would imagine you might be better with a crop that doesn't involve too much digging, so both compost and sclerotia are near the surface rather than deeply incorporated, so I'd avoid potatoes. Sweetcorn would probably do the trick. Wheat being an obvious candidate for a commercial onion grower.
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All of your comments are very informative and helpful.
I'll add a couple of points:
- my leeks have not been affected (in the past).
- only two out of a dozen garlic were affected.

NaturesBabe: Here we had the very dry spring followed by a wet early summer. Soil is clay and chalk but as the allotments are on a slope drainage is fine, the soil stays wet but never water logged. The area where the onions were growing is heavily manured.
Sincerity: Good solution, but the part of the allotment I used this year is "open-field" and I can not see that I can get sufficient soil/manure in the cover the lot.
Regarding the trials to rid the soil of white rot, I tend to agree with Alan; if they had been successful, we would have heard.

On the positive side: onions are cheap enough to buy! I'll just have to fill the slot with something else.
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I have had a good sort through the onions. I think that between a quarter and a fifth of them were affected.
I cut the affected bits (mostly small areas) out and those bulbs have been reduced to onion "marmalade".
I wondered about using a pickled onion recipe with chopped material. Anyone tried this?
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Colin_M
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I'd seen this thread and thought I didn't have to worry about it. Not so sure now.

When lifting my garlic today, I found a small number where the stems had rotted off and the bulb was in various states of crumbling or rot. It's been very dry for most of our 2011. Despite this the garlic has grown quite well and only recently developed any rust.

This is what it looked like. Can anyone advise if this means I shouldn't plant alliums in this part of my plot for a few years?
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Stephen
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Very informative pictures. That is as bad as the worst of mine.
The sad side of the news is that it was the first time I have tried garlic and in general they did well. My onions were the best ever, helped, I am sure, by the hot, dry spring.

Question: Am I right in thinking that in dry summers the rot does not attack? (or is substantially reduced in virulence)
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Nature's Babe
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Hi Diane, beneficial fungi and bacteria have a function in suppressing disease, but it does involve a whole new way of thinking about gardening.
Sit down before a fact as a little child, be prepared to give up every preconcieved notion, follow humbly wherever and to whatever abyss nature leads, or you shall learn nothing.
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Catherine
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Mine are just starting to show signs, we lost all our shallots. Though I know mine are not ready to pull up would it help to pull them now before they get any worse, even though they are not quite ready. Alot of them look quite good at the moment, the ones further away from where the shallots were. I don't really want to lose the whole bed waiting for them to be fully ready as some of them are really a nice size.
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