Soil infection

[Ger-annie-um]

We're in the process of re-building our 3 raised beds (frames rotted). I can't grow any onions or garlic in these beds because of onion white rot. We had a thought that, because we have to dig out soil in order to get the old frames out , what depth of soil we'd need to dig out in order to get rid of the infection. Anyone have any ideas?

[bikermike]

what would you do with the soil dug out? aren't you at risk of creating a larger area of infected ground?

[Ger-annie-um]

what would you do with the soil dug out? aren't you at risk of creating a larger area of infected ground?

Ah, that's not a problem. We have a large patch of garden that needs soil, it only has odd shrubs in it and it will never be used for veg or alliums. We were thinking of buying in some soil for there but if we can relocate the soil from the raised beds we can use the fresh stuff on the beds. That was the plan anyway. Happy to be corrected if it's not a good idea

[rary]

I honestly don't know the answer to your question but if I had that problem I would go down 2 spade depths which I recon would be at least, 18inches. but as I said I don't know if there is any recommendation for such work I do know that there are community gardens near by where they covered poisoned ground (industrial) with membrane then built raised beds on top of it

[Ger-annie-um]

Thanks for responding Rary. I've done a bit more research and it appears the the sclerotia? need to be within 1 - 2 inches of the root of the alliums in order to detect them. For onions/garlic that would be around 6" deep, leeks obviously a lot deeper so your guess of 18" wouldn't be too far out. I'm going to take out 12" and mix in a lot of mpc as, apparently, the sclerotia doesn't live in mpc. I've used garlic granules at the allotment with some success so I'll use that too. I can only try..............and live in hope.

[ameno]

In theory, the above suggested 18" should be plenty.
However, the problem is white rot spreads very easily, and if even the tiniest bit remains, it will reinfect easily. It can persist in the soil 10-15 years, so you will have to be very careful to avoid any cross-contamination from the bed you move the soil to. All boots and tools would need to be washed before they go anywhere near any veg beds.

I have heard some people have had good success with greatly reducing white rot infection (it's basically impossible to completely eliminate it) by digging garlic powder into the soil periodically in the first year (best applied when air temps are between 14-19c), then planting onions in the second.
The dormant fungal bodies in the soil respond to chemicals in any allium (which are obviously in the garlic powder) and germinate, but then, finding no host, they die off. This apparently greatly reduces the level of infection in the soil, and thus the chances of infection.

[Ger-annie-um]

Ameno.........Good point on transference I'll be sure to remember it.

I've used garlic (granules not powder) before with some success. You need to water it in well and, I was told, the soil temp needs to be around 15c

[toomanytommytoes]

Here's a quite recent study on the effects of 'sclerotial germination stimulants' on the incidence of white rot. They trialled onion powder, garlic powder, onion oil, garlic oil and Allium waste (ground up peels of onion + garlic).

https://www.sciencedirect.com/scienc...05844018367136

[Ger-annie-um]

Here's a quite recent study on the effects of 'sclerotial germination stimulants' on the incidence of white rot. They trialled onion powder, garlic powder, onion oil, garlic oil and Allium waste (ground up peels of onion + garlic).

https://www.sciencedirect.com/scienc...05844018367136

This was very interesting, although I didn't really understand most of it.............science gene passed me by. I think from this it would appear that garlic oil would be more effective that granules/powder. I'd be happy to give it a try if I knew the dilution ratio.

[toomanytommytoes]

Interestingly it looks like the allium waste had the greatest effect, followed by the oils.

I've seen elsewhere a suggestion that 1 whole bulb of garlic blended into 10 Litres of water will cover 2 square metres of ground. Best applied when the soil is warm in spring.

[Mark_Riga]

My impression in my garden where I do have white rot, is that it starts to be active from early june onwards. So if I was going to try applying 'sclerotial germination stimulants', I would do it in early June and then possibly July in the Year before growing.

[Penellype]

Interesting. I have white rot at my allotment, although it didn't show in the first year, possibly because I had just filled the raised bed to a depth of about 6 inches on top of cardboard. I'm trying the same thing again this year (in a different bed) but the garlic idea sounds great for next year's onion bed.

[Scarlet]

I had to give up growing garlic, leeks and onions completely. It was so upsetting to see the whole lot go.
I now only grow elephant garlic in my flower borders. I tried the garlic blended in water method with limited success so I chose to stop growing it in my veg beds.

Anyway, good luck on it and let us know how it goes. Fingers crossed for you.

[Aberdeenplotter]

Why not leave all the soil in place but sow calliente mustard in the bed. Before it seeds, chop it up with hedging shears or similar then fork it into the soil. It then releases a natural fumigant which I'm led to understand kills off the infection.

[rary]

Just reading through this thread again and from the comments given I would try scattering the allium substance of choice covering the soil with plastic to help the soil temperature to increase (or vice versa) then follow with the calliente mustard and again if necessary cover with polythene to keep the soil warm to allow the fumigant to work and hopefully clear the soil in a yeara