Onion White Rot -- Again!!!

[DiG]

I think I am going to have to give up on growing onions and garlic This is the second year running that I have lost most of my crop to white rot in spite of growing in a completely a different part of the plot, as far as possible from last year.

I carefully destroyed all of the infected plants last year and didn't compost any material/weeds etc from that bed but is it possible that it has been spread by my compost despite my best efforts? If that is the case then none of my beds will be useable for any alliums for a long time - there seems to be some difference of opinion as to how long, from 5 years to 18 years. Also, won't I be perpetuating the problem by composting plant material from anywhere on the plot from now on?

The only way I could grow them is in troughs of bought compost - which is really not cost effective given that onions are relatively cheap to buy. Might try it for garlic though.

Diane


Diane

[Stephen]

I suffer too. This year I had the best onions I have ever grown but still had some white rot, sadly.

[Nature's Babe]

Are you both in rainy areas? Not sure if this might help, but I plant my onions in the autumn and often we get a lot of rain overwinter but they are in raised beds which helps drainage and so far no problems, then again come spring we had drought not more rain, I just wondered if you had tried growing them in raised beds?

[DiG]

Hello NB. I do grow all my vegetables in raised beds although they do have wooden frames unlike yours.
I grow from sets planted in the spring as the ground can get waterlogged overwinter. I am very close to the river with a very high water table and once the ditches get full there is nowhere for it to go. However this was a very dry winter for us and the ditches didn't get full at all.
I did successfully grow onions and garlic the first two years we were here with no sign of white rot at all. I might give it one more try in the bed I first grew them in 4 years ago.
What varieties would you recommend?

Thanks, Diane

[alan refail]

Hi Diane

Forget about rain and raised beds and planting times. If you've got white rot you've got it for a long time, as I know from experience. Mae'n ddrwg gen i

http://apps.rhs.org.uk/advicesearch/pro ... px?pid=226

[Nature's Babe]

Would a biofumigant like caliente mustard be worth a try, you could grow t overwinter to clean the ground where you are going to plant before planting the onions, it might be worth a shot.

http://www.greenmanure.co.uk/caliente_mustard.htm

[DiG]

Hi Alan, I'm sorry too I'm afraid my Welsh is limited to the National Anthem and Calon Lan. Thanks for the link, it is much as I thought. Do you still grow onions etc anyway?

Hi NB, it certainly couldn't hurt to grow the caliente mustard anyway. I'm sure the ground would benefit as these beds were dug from what was part of a field that had been untouched for many years. The other two beds in this section had green manure grown on them over winter last year and this has certainly improved the soil. These have brassicas in at the moment and are doing really well.

Thanks, Diane

[Nature's Babe]

Remember to incorporate it into the top layer as soon as you blitz it up Diane, any delay and you lose the fumigant benefit into the air instead of getting into top layer of your soil.

[Beryl]

Remember you can also pass it on by treading on your infected beds.

Beryl.

[realfood]

I am trialling an organic control for white rot using ground up garlic to trick the white rot sclerota into growth and then dying as there is nothing to feed them.
Possible Organic control of “white rot”.

This method of organic control of white rot was suggested by Professor Fred Crowe. Oregon State University, after ongoing tests.

When white rot has infected an allium bulb, it forms thousands of little black seed like, “sclerotia”, which fall off and remain in the soil, unless the infected bulb and the adjacent soil have been removed and sterilised. When the “sclerotia” infected ground is dug over, the “sclerotia” will be distributed throughout the digging depth. These sclerotia will become dormant over the Winter, but in the Spring will germinate as soon as they sense the presence of allium roots close by.

The control method is to trick the dormant “sclerotia” into thinking that there is an allium growing beside it, by watering on a ground-up garlic bulb solution of 1 part garlic solution to 1000 parts water, say one ground-up garlic bulb to a watering can of water. This should be watered onto 1 sq m of damp soil. It is best to be watered onto the ground when rain is expected, so as to take the garlic water deep into the soil to contact the maximum number of “sclerotia”.

Strip the garlic cloves of their papery wrapping and cut off the basal plates before you grind the cloves up, to cut down the danger of introducing any disease. You should be able to taste and smell the garlic in the solution. It should be applied when the ground temperature is between 10c and 20 c with an optimum temperature of 15c.

It should be watered onto the ground that you intend to use for alliums, during the preceding year while the ground is moist and warm.

It is also possible to use garlic powder which you can find in equestrian stores or on-line, as it is used for the treatment of horses. This should be applied at a rate of 250 lb to the acre. Roughly 125 Kg per 4000 sq m, or roughly 30 gm per sq m. This has the advantage of having been sterilised and unable to pass on any allium infections but is not so effective.

Once the sclerotia have been tricked into germination by the garlic liquid or powder, there are no alliums for them to feed on and so they die, thus breaking the reproductive cycle of white rot.

[Johnboy]

Hi Realfood,
There was a trial a few years ago here in UK using chopped onion pieces which was supposed to have the same effect as the Garlic on Oregon Trial.
Being parts of Onions they attracted the sclerotia from the soil and when the parts of Onion shrivelled and died it was said to take the sclerotia with it.
Sadly like all trials of this kind you read the start but miss the conclusion so I am afraid I do not know whether it worked or not.
My thoughts are that it must have failed because otherwise it would have been quite a breakthrough and shouted from the rooftops.
JB.

[Stephen]

I think I need to see more pictures and read more, so that I can determine if this is just rot (it has ben pouring down ever since I complained that the weather had been too dry!) or Sclerotium cepivorum.

I've been reading this page http://www.omafra.gov.on.ca/english/crops/facts/95-063.htm#Root%20and%20Bulb%20Diseases but I am not much clearer.

The rot I have does affect the garlic too. Not all plants for either the onions or garlic.
It covers the bulbs in white and softens the outer skins.
There are none of the black "structures" refered to on the RHS site.

[sincerity]

When I first took on my allotment (some 7 years ago), I didn't realise that the soil was contaminated with white rot. My first experience of this problem was pulling up an onion, only to find the base of the onion still in the ground, but the leaves and top of the bulb in my hand! Very disappointing, especially when there is often no sign of trouble, with onions appearing otherwise healthy. When I sought advice, I was told that this rot could persist in the ground for in excess of 15 years. I was advised not to grow any alliums in the ground ( as not to perpetuate it ) and to be careful not to transport the rot to other parts of the garden by means of soil in the cleats of garden boots or soil on tools. I found this almost impossible to achieve.
Given other ground based problems, e.g. club root, frost zones; I found that rotation plans would become a nightmare. This is what I did, it has worked for me. I garden organically and now produce large, healthy onions. I bought some black weed suppressing membrane, which I placed on the soil to be used. I added a 2 tier 'link a bord' raised bed set and filled it from scratch. Although the rot will still be in the ground, it has never escalated into the beds. Interestingly, I have never known water run off to spread it onto my lower garden tier.
For information, I grow onions from seed. I use green manures when the beds are empty after the summer crops - usually I choose phacelia, vetch and left over peas. I dig these in. During winter I add manure, dig in before planting. I feed with maxicrop at intervals when onions become larger. I live in the upper Valleys, where rainfall levels are exceptional.

[Nature's Babe]

This link would appear to fit in with sincerity's experience and my suggestion

http://www.gardenorganic.org.uk/organic ... hp?id=1700

maybe soil fungi play a greater role in soil health than we currently understand, I don't understand the science of it but am happy to see my healthy veg growing alongside occasional fruiting bodies of fungi, I see little white fungi, little grey ones, butter coloured small ones, and see them as helpful and so far causing no harm to any plants which thrive alongside them. Fungi thrive in organic conditions.

[realfood]

Hi Realfood,
There was a trial a few years ago here in UK using chopped onion pieces which was supposed to have the same effect as the Garlic on Oregon Trial.
Being parts of Onions they attracted the sclerotia from the soil and when the parts of Onion shrivelled and died it was said to take the sclerotia with it.
Sadly like all trials of this kind you read the start but miss the conclusion so I am afraid I do not know whether it worked or not.
My thoughts are that it must have failed because otherwise it would have been quite a breakthrough and shouted from the rooftops.
JB.

It appears to have been successful, as there is now a shortage of the onion waste for farmers to use. I think that some of the chemicals that farmers used to use to control white rot, are no longer available in the EU.http://www.farmersguardian.com/fighting ... 30.article