[Carollan]

Ok,so we can`t compost any plant matter to do with onion white rot,sensible.....how do we know that people who send their plant matter to the compost makers through their brown bins in the UK don`t add all sorts of white rot matter?

am I becoming paranoid,do these compost makers create a heat great enough to kill anything to do with white rot?

otherwise we cant use ANY compost  safely,can we??

I am taking out a huge chunk of soil from the 2 onions that had white rot in my patch and hoping that there is no more.....

[Yorkie]

Commercial / council composting certainly does get very hot but whether it's enough to kill off fungal and other spores I'm not sure.

[Trillium]

I'm of the same opinion, Yorkie. Home composting is somewhat hither and thither by comparison to commercial composting that gets hot enough to cause serious skin burns. The onion rot spores thrive in cool, damp places and a commercial compost heap will kill them flat.

While you might get rid of the actual diseased plants, you'll still have the rot fungus living in the soil, so care must be taken to carefully rotate plants and avoid putting any alliums (garlic, shallots, onions, chives, leeks, lilies, etc) in that area for at least 3-4 years. Also clean off boots, tools, gloves, etc. used in infected areas so not to spread the spores.

Sadly, the wet UK summers make the whole onion rot problem worse as the fungus thrives in damp conditions.

[heloise]

Before we got the allotment we had a small patch in the garden to grow things, including onions, successfully. Then we built a small raised bed area and filled it with commercial compost. Voila - white rot on the first onions we grew in there. I'm convinced it came from the compost. So perhaps it is not possible to say all bought compost will be white rot free.

[bigben]

I took over my allotment last year after it had been left untended for years. My first onion bed had about 40% white rot. I turned it into a fruit bed and sowed winter onions and garlic in another location only to find the same situation. I dont know how my summer onions will do but I am not hopeful.
   I came across this idea http://www.dgsgardening.btinternet.co.uk/whiterot.htm
where garlic powder is watered into the soil this tricks the spores into germinating only to find no real onions or garlic to host them so they then starve. The theory is that if this is applied for a few years in a rotation then it should improve the situation by removing the spores. I bought a 3.5 Kg tub or garlic powder from Amazon and plan on doing every bed on my allotment at some point this year, then again next year.
    Hopefully this will improve the situation.

[Brewers]

According to the RHS, the 'spores' (there not actually spores in the trad sense I think) won't survive at temps much above 20 degrees. Commercial composting (ie fast) would I'm pretty sure create temps much higher than that (they will be composting all sorts of materials.

I think more likely, the sets purchased have white rot in/on them, having been grown on in contaminated soil or you've transplanted the 'spores' via your tools, hands, shoes (it's not an air borne fungus like blight for example).

I too am treating with garlic powder and I am going to try armillatox too on one bed only. My contaminated bed will then be fallowed for three years and treated each year again with garlic powder (I like to rotate a fallow bed, but I'll have to sacrifice this I think over the next few years).

[DD.]

I would remind people at Armillatox is licenced only as a soap based cleaner.

The used of it on soil to kill not only diseases, but also worms etc. cannot be condoned by this site.

[Trillium]

I agree DD. Many reference sites condemn the use of Armillatox on soil as it acts more like a poison than anything else.

[realfood]

I do not think that 20C is nearly enough to kill the white rot "sclerota". The published literature suggests that the "sclerota" are most likely to germinate when the soil temperature reaches between 10c and 20C. This is why the white rot fungus only becomes evident once the soil temperature reaches this level.

[moose]

Had exactly the same experience as heloise. Bought in a tonne bag of compost (not from e-bay) and first crop of onions had white rot. A friend has told me that they have been using calient mustard as a sterilant has brought an improvement.

[Carollan]

Thankyou all for your ideas.I do rotation anyway,so that`s not a problem.I shall try the garlic `wash` as well.

Only 3 side by side onions had the  rot,will the others get it too?


Carollan

[Yorkie]

The pathogen can travel through soil water, I believe, so there is a risk that it could spread.  There is also the risk that you can transfer it round the plot on boots or trowels etc.