Garlic granules and manure for white rot?

I had an amazing crop of onions this year,the first time in many years,on a plot obviously not infested with the sclerotia of white rot.
I was moving on next year to a patch I know has it.
I was thinking of using garlic granules or powder,lots of manure and a plastic cover to try and get the sclerotia to grow now,in the next few slightly warm days left .

Have you ever tried this sort of idea?
If you have been successful using another organic route,PLEASE tell me.I adore home grown onions !

I've used garlic powder to good effect but always applied in mid summer. Keeping the soil warm with sheeting seems a good idea though and worth a try, for the price of garlic powder I'd say go for it.
Re onions, Golden Bear from seed are the variety of choice for us. Marketed as resistant to downy mildew but in practice is also very resistant to white rot. Nice flavour and stores well too.
Sadly haven't found a red onion with quite the same qualities.
The most successful garlic for us is self saved. A happy accident originally from supermarket stock, turned out to be an early variety so is often harvested before white rot gets into full swing.

as we are on the subject of Garlic granules for some time now I have been experimenting with garlic spray for brassicas i know i have mentioned this topic on this site several times but i have to admit I haven't had much success this season with garlic spraying but I'm not going to give up

it seems that the Garlic treatment for white does actually works ? so how to improve my garlic mix for spraying brassicas that is the question because I'm not quite sure if I have the rite mix because I'm using garlic powder not granules and the powder is probably not a strong enough mix I also added some chilli powder sugar and a squirt of washing up liquid and although I thoroughly sprayed the crop with a normal pressure sprayer it maybe didn't cover the underneath of the plants as it should have  ?  the spray had no effect on the plant growth

so its back to the drawing board interesting to note with your process using garlic granules for white onion rot I gather you need to spray or other methods directly on the ground or soil perhaps I also need to spray the ground with my garlic mix when spray the brassicas ?

as i said I  have been using garlic powder in the mix maybe i need to go with garlic granules instead  I'm trying to get more towards organic instead of chemical spray and your comments on this topic very welcome