My garlic has white rot, that’s it. That’s the second bed that I’ve had it in and I’ve got a horrible fear that I’m the one that transferred it, there is some relief in the thought that it was in the ground already as it appeared in the first year of my old (new) plot. It does, however, mean that I’m never growing garlic (or onions) in that bed ever again, and probably not in any of them. One of the troubles with white rot, apart from the damage that it does to the bulbs is the fact that it can stay active in the ground for up to 10 years.
Once it’s there, it will be a long time before you’re able to plant any onions, garlic, leaks or any other alliums for that matter. White rot is a serious disease that’s spread by the soil borne fungus Stromatinia cepivora that will usually become apparent from mid-summer to Autumn, just when you’re thinking that you’d like to harvest. If you’re lucky then you’ll be able to get the onions before they get too damaged and as long as they’re not too far gone, they are still usable.
If you store them all together though, you’ll need to keep an eye out as the rot can persist and damage the whole crop. Anything else that you need to dispose of must be burned as the fungus spreads very easily. You’ll know when you’ve got it as there’ll be a fluffy white fungus around the root of the bulbs with little black structures in it, this is what differentiates it from other less troublesome issues like mildew or mould. It can be fairly localised in the ground and it’s not a sign that all of the crop will be affected but once it’s there, the only thing you can do is make sure that it doesn’t spread. This is going to be a case of good hygiene and crop rotation, you’ll be ill advised to be planting onions in the same place twice, especially if the rot has set in. Crop rotation is the best practice for any ailments that are likely to befall your crops as many plants don’t suffer from the same diseases. If you change the location that you crow certain things each year, you’ll be reducing the change of anything persisting in the soil.
As the only cures that are available for white rot, apart from time itself, are to sterilise the soil with a chemical arsenal, I’m going to leave that out. Many issues that are preventative ultimately become a problem themselves, so just let nature do it’s thing and it will all work out in the end.