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Author Topic: onion white rot  (Read 425 times)

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jambop

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onion white rot
« on: August 11, 2017, 14:40 »
My onions are drying off just now and while I have some very nice onions I have lost some to white rot. Now this is, I think, quite strange. I have grown my onions from seed and then thinned into modules and grown on prior to planting out. I have also bought some onions from the market which are bare rooted and planted them out using a dibber and then levering the soil back against the roots on four sides so they are very firmly planted not one of those onions has had a problem. I am wondering if the relatively loose planting of the modules has something to do with it? Or is it more likely that the compost I used has not been sterile and the spores have been in that? Another factor may be that just prior to them being lifted we had quite a lot of damp weather could that have had some effect we had a lot of hot dry weather before that. I do think that next year I am going to grow my seedlings on until planting time and then firm the soil a lot more and dib the plants in bare rooted taken from the seed trays they definitely seem to do much better when planted firmly. I think the compost module leaves a pocket that can when rain arrives act as a damp sump and encourage fermentation as the sun heats the soil around about. It is curious though that any onions I have planted out using the dibber technique have given me any problem this year or in any other years previous. Also it is interesting that I had no problems with my garlic or for that matter my leeks.
« Last Edit: August 11, 2017, 14:43 by jambop »


Christine

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Re: onion white rot
« Reply #1 on: August 11, 2017, 18:23 »
I have a nasty feeling that once you have white rot on site it will stay on site. Your best option is to look for onions which have some resistance to it. They can be found and do reasonably well. An allotment neighbour manages to grow decent onions going down that road (and I believe using lime).

mumofstig

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Re: onion white rot
« Reply #2 on: August 11, 2017, 18:42 »
IIRC you often plant seedling onions bought in the market?
You have probably imported onion white rot with the seedlings.

Even if you stop growing onions it lasts in the soil for up to 20years. Bad news  :(

Have you got a pic or did you see the black dots of Onion White rot/the sclerotia  (like seeds these carry over from one crop to the next to spread the disease)
You may have basal rot, which likes warm but wet conditions.
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Mr Dog

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Re: onion white rot
« Reply #3 on: August 11, 2017, 21:15 »
Quite a few plots on my site have white rot the owners of which grow the variety Golden Bear (from sets and seeds) with quite a bit of success - last year those who grow them reckoned 80-90% of their onions survived to go into storage.

Paul Plots

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Re: onion white rot
« Reply #4 on: August 13, 2017, 01:54 »
Damp conditions can cause white rot of onions to trigger an attack of the white fungus that appears around the roots and base.

Once in the soil it does, as has been said, reoccur when ever the onion family are in that patch of ground. It is easily spread... as simply as walking on infected soil and into a new area.

Avoid planting in the same spot.... could try increasing drainage or using a narrow raised bed and putting compost in but... it's fighting a losing battle.

My dad had it on his plot - we tried to avoid using the same spot but it spreads. Still grew onions but knew they had to be lifted at the first sign of harvest nearing and damp conditions. Most of crop was fine but keeping qualities much reduced.

I think there are chemical treatments that can help reduce white rot but preferred not to use any.
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jambop

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Re: onion white rot
« Reply #5 on: August 13, 2017, 11:15 »
To be honest I am just assuming it is white rot although the onions do not have a lot of white fungus on them. The plate where the roots come out tends to rot away and has that horrible sour smell to it. Many of the onions are un affected and look very good as well as having grown very large as well. I have attached a photo which shows the typical damage. It is interesting that the red onions are more affected than the yellow ones. The onions I get from the market are un affected and to be honest I really do doubt they would be the culprits for brining the problem they sell thousands of transplants each year if they were known to be spreading plant problems they would be out of business pronto.
DSCN3453.JPG

Paul Plots

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Re: onion white rot
« Reply #6 on: August 15, 2017, 00:58 »
Prolonged damp ground appears to make matters worse.

A raised bed might help perhaps.

victoria park

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Re: onion white rot
« Reply #7 on: August 15, 2017, 09:18 »
Hygiene wise I find it just impractical to follow quarantine methods 100%. Most years I get a bit of it, say 10%, with the odd really bad onion, but the 10% are usually edible if not suitable for storing.
I am careful at the harvest stage, that's important, and the composting, no onion peelings ever go to compost, but that's about it. I now keep to a reliable set supplier and no longer buy cheap sets from Wilko. With importing the problem in mind, more and more of my crop also comes from sowing seeds now, but that presents its own problems earlier on.
Haven't used the same beds in six years, with a few still to go, and record details on the spreadsheet for future reference. This year is just about 100% free.
The onion bed site is my first consideration each year. I feel the rot is another good reason to practice more of the "no dig" method and this definitely has improved the incidence. No point in unearthing the devil any more than necessary. I don't know if it makes a difference, but my instinct tells me not to put down plastic over the Winter.

It seems to be one of those diseases that are part of allotment life. A case of managing it as best one is prepared to, and trusting to good fortune.
« Last Edit: August 15, 2017, 09:33 by victoria park »

Enfield Glen

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Re: onion white rot
« Reply #8 on: August 15, 2017, 10:48 »
I to have been suffering with the white rot for a few years now. This year I tried Goldern Bear from seed and so far it looks to be a success, only 2 appear to have been affected. Red Baron sets seem to have been badly affected and these also started going to seed early in the year over 50% lost. A pre treatment of the bed with lime also seems to have approved results.

jambop

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Re: onion white rot
« Reply #9 on: August 15, 2017, 17:02 »
I to have been suffering with the white rot for a few years now. This year I tried Goldern Bear from seed and so far it looks to be a success, only 2 appear to have been affected. Red Baron sets seem to have been badly affected and these also started going to seed early in the year over 50% lost. A pre treatment of the bed with lime also seems to have approved results.
I have grown golden bear this year and will be doing so again next year. I have some very nice onions and they do not appear to be affected as much. One other thing I am going to do it actually plant out my onions later when the temperatures are higher So plant them out some time in May still lots of time for them to grow and dry off.

fatbelly

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Re: onion white rot
« Reply #10 on: August 16, 2017, 14:52 »
How do commercial growers combat White Rot !! For us its a pain but for commercial growers it's their livelihood .
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Paul Plots

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Re: onion white rot
« Reply #11 on: August 17, 2017, 02:59 »
How do commercial growers combat White Rot !! For us its a pain but for commercial growers it's their livelihood .

Good question........ Careful choice of set or seed to start with and I guess they don't grow onions in the same location each year as they have more space to choose from. Also I expect that farmers growing onions on a large scale are those who have the right soil conditions for onions... good drainage and a warm dry period towards harvest... not that the weather can be guaranteed anywhere.

Farms on heavy clay probably focus on other crops.

 

jambop

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Re: onion white rot
« Reply #12 on: August 17, 2017, 11:10 »
I suspect they will have the option of a fungicide deemed far to dangerous to let common or garden allotmenteers on the loose with ... most farmers are ex rocket scientists and brain surgeons dontcha know.

 


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