[Jelliebabe]

Hi Guys

I had what I assumed to be white onion rot on my onions last year.  I am of course not growing them in the same spot this year but how long should I leave it before they go inthat bed again?  Will this affect my whole plot do you think?

HEYULP!

JB

[BabbyAnn]

A minimum 7 years and even then, are you sure? And that includes garlic, chives, spring onions, shallots, leeks ...

Also bear in mind that when digging beds, your tools and boots have probably spread spores across the plot anyway, and do you really know what's in your compost?  

All you can do is make a note of hot spots and avoid them in future, but it is a bit of a lottery and all the more sickening when the onions are bulbing up nicely and then find them go down.  You might be lucky, or you may find after trying for a couple of years that it isn't worth spending all that time growing onions.

[Kleftiwallah]

I have read either here or 'other forums' that watering the area with a liquid made from onions/garlic/leeks may cause the spores to 'come looking' and die off as there is nothing substantial to grow into or feed off.      Sounds a bit crazy, but it may just work ! !  ! !     Cheers,     Tony.

[bigben]

I have read either here or 'other forums' that watering the area with a liquid made from onions/garlic/leeks may cause the spores to 'come looking' and die off as there is nothing substantial to grow into or feed off.      Sounds a bit crazy, but it may just work ! !  ! !     Cheers,     Tony.

My allotment suffers from whiterot badly. Every bed I have grown onions or garlic in has shown whiterot. This year I am using a bed that others on the site say has not been grown on for years and hoping it is not affected. But, as others have said you transfer spores on tools and your boots so I am not holding my breath.

As Kleftiwallah says - I also read what he read and have bought garlic powder and started to water it into a bed I might use for onions next year. The theory being the smell from the powder fools the spores into germinating and they then have only the "garlic smell" to live on! They then die and next year the area is less prone to whiterot. I will let you know if it works but I suspect it will take a few years to make any significant improvement.

[mumofstig]

It's too early or too late whichever way you look at it, to spray now. Soil temp has to be above 15C

Root Exudate Solution (before planting)
A solution to stimulate the sclerotia to germinate in the soil can be made using onion or garlic juice using culls from your crop. Once the sclerotia are stimulated and germinate they then die due to lack of nutrient reserves because the garlic is not actually present. The optimum conditions for germination of sclerotia occur when soil temperatures are between 15 degrees to 18 degrees C. Garlic works better because it's stronger than onions. An effective dilution for garlic is one to a thousand parts garlic and water. The idea is to somehow distribute it over the area that you're going to crop in the future getting this juice stimulant concoction across the area and down into the soil. It needs to get it as deep as you've tilled it. ............ Garlic powder that's tilled in at 250lbs/acre has also been used.

advice taken from this site
 
http://www.bcseeds.org/white-rot.php

[Trillium]

In the US, commercial onion growers won't grow onions on an infected field for 15 years. That's how determined those disease spores are.

[Yorkie]

I had always heard 20 years ...

[DD.]

RHS say 15....

[shokkyy]

Is it true that you can only get white rot if it's imported on contaminated sets or something? So if I always use seed for onions and only use garlic cloves replanted from my own crop, I should be safe from infection given that I'm growing in a self-contained environment, i.e. my garden?

[Trillium]

This says it better than I can:

http://www.organicgardeningpractices.com/onionwhiterot,php

[realfood]

I have already posted this method after having great success with it last year. You haave nothing to loose and everything to gain.
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”.
After carrying out the first treatment using the ground-up garlic water, turn over the soil with a fork. Then apply the ground-up garlic water again. This will enable the soil to be treated to a fork depth, hopefully killing most of the white rot 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 as using fresh garlic bulbs.
 
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.

[Yorkie]

I was just wondering whether anyone who tried the garlic drench had had any success.

Did you have a heavy infestation of white rot previously, realfood?

[mumofstig]

farmers do something similar
http://www.farmersguardian.com/fighting-allium-white-rot-and-the-uk%E2%80%99s-waste-problems-with-composted-onions/23430.article

at the bottom of that article they also talk about basal rot which some sets may carry, rather than us all having white rot on our plots. Seeds would seem to be the best way to go.

[Yorkie]

I do suspect that any onion rotting is immediately ascribed to white rot, same as any marks on tomatoes and potatoes is immediately ascribed to blight - whereas in many cases it may be a different pathogen but it's the first thing we all think of.

[Kajazy]

I've also been battling with voracious white rot on my plot - and it's definitely there as I have seen the little black poppy-seed-like sclerotia on the rotting alliums - but I am trialling the garlic drench on a large patch of ground (I watered it in at the end of last summer, turned over the ground and then watered it in again - the soil was warm throughout the process) - I'll let you know how I get on, as I'm still determined to grow my leeks, garlic, onions and shallots. BUT, I would just like to add that in spite of the white rot on the plot last year, I still managed to get enormous amounts of usable onions and leeks (didn't plant anything else) from the ground - in fact I had a home-grown leek & potato soup tonight! The main thing is that you can't store onions/garlic/shallots in the usual way - I just dug them up, peeled them and chopped them up in the food processor, then double bagged them and popped them into the freezer just as they were - they have been invaluable for all my winter stews/bolognaise sauce/cottage pie etc etc, and have saved precious minutes in preparation time of an evening. So, in my view, you can live with white rot if you have to. A bit like I live with white rot, canker, horse tail, creeping thistle...etc etc etc...