2024 garlic harvest - smaller bulbs due to rust?

Hi all,

We've pulled our autumn-planted garlic plants recently and are drying them outside during the daytime (much to the bemusement of our neighbours). There are still a small number of spring-planted garlic plants in the ground and we will pull those in a month or two.

The autumn-planted bulb are pretty small this year and I believe its due to a lot of allium rust. Our autumn (fall), winter and spring seasons were all much wetter than usual (climate change, sadly, is becoming much more evident in my part of the world) and I suspect that is part of the problem. We usually get rust on our garlic towards the end of their growing season but it hasn't been as bad, nor seemingly impacted bulb size.

I'm going to dispose of the foliage elsewhere to try and limit the spread of the rust spores via compost. I've not decided on the best way to do this yet - I'll either burn them, to return some of the nutrition to the land via the ash, or I'll put them in our municipal green waste for industrial composting.

I've never bothered to remove leaves as the rust appears and perhaps, next year, I should try doing that too. It always seems like one task too many in the busy part of the year.

Hi Luke,
Were there any symptoms other than the smaller head? I'm not familiar with rust on garlic, and would like to know how to tell that from the problem simply being a wet year with little sun?

I always thought rust was more a dry weather thing, but presumably not. You live and learn - looks like something I will have to look forwards to then!
Is removing leaves to prevent spore propagation or trying to protect the existing crop? If the latter I would suggest doing half and leaving half, then you'll see if it affects the yield.

I did a bit of internet research....

Edible backyard says these things may help:
plant early,
give appropriate nutrition (excess nitrogen can exacerbate the problem),
don't plant all in one block - sometimes one area is affected and another will stay clear,
mulch to prevent soil splash,
spray with competing organisms (seaweed tea) or possibly with milk
practise crop rotataion and leave as long a gap as possible between allium crops
don't compost affected leaves unless you can achieve temperatures to kill the spores.

I suspect you could put the leaves where there are no alliums and it would do no harm - like under a hedge?

I love your picture of the garlic drying in the front garden!

Here in New Zealand, I am very familiar with garlic rust. As the disease has spread over the last few years, garlic has gone from an easy-to-grow crop with few problems to something many gardeners are struggling to get a return from. In the worst year I've had thus far, I planted 25 cloves outdoors, had only 10 plants survive, and all of those rounds rather than full heads. Rust is seriously bad news!

Rust spores live dormant in the soil for some time, so will cause problems for years to come. However, those soil-borne spores can only reach the leaves if moved there, typically through splash action during rain. This means you can significantly reduce the spread of disease by heavily mulching with non-infectious material, irrigating with ollas or drip tape rather than overhead watering, and, in the extreme, shielding the plants from rain by growing them under protection (a cold frame, tent, or glasshouse). We have a damp climate and serious rust issues in my current location, and I have had to take to growing garlic in the glasshouse if I want to do more than just break even in terms of numbers of cloves. And I did just break even for 4-5 years after rust came along -- nearly gave up growing garlic at all before discovering that mulching and protecting from the rain were the key to actually getting some garlic out of my garden.

This disease has seriously knocked back commercial garlic producers -- locally grown garlic has gone from NZ$12/kg to NZ$40/kg over the last 5-10 years as large-scale growers struggle to manage it.

Best of luck! Hopefully my lessons learned mean you don't need to go years without a good harvest like I did!

Thanks for the comments everyone. Last year, which was drier, rust was much less of a problem.

I think I'll take the following approach:

- not composting the material, or doing so far away, perhaps under one of the new hedges as Nancy suggested. Last year I did compost the material and, despite my best efforts, I doubt my compost was hot enough to kill the spores
- spacing the plants a little wider next year
- mulching between the garlic plants next year. We usually don't mulch much during the growing season as our main pests are slugs and the mulch provides ample habitat for them to shelter under, during the warmer days. The alliums don't seem to be affected by slugs, however, so I could make an exception for them. Note that we do mulch over the winter to feed and protect the soil.

The idea of adding competing organisms is an interesting one too. I've not ventured far down the path of boosting soil/foliar microbiome, just occasionally adding a slap-dash concoction of things I believe will foster lactobaccilus (such as past-best milk, starchy water from rice or pasta, leftover sauerkraut or kimchi water). I will look into this too!

Interestingly, my broad beans have rust too (a different species, unrelated to garlic/allium rust). I've never had a problem with this before.

Removing rust-affected leaves early can reduce spore spread and severity. Yes, trying wider spacing is the best practical solution you can do. Also there is a rust-resistant variety called Georgian Fire. It is a very decease resistant variety. If you can find try that.