Our garlic has Puccinia allii. Big. Sad. Sigh. This a fungal disease that affects plants in the Allium family (onions, chives, leeks, garlic etc). Commonly called ‘garlic rust’ it starts on the foliage of the plants (the leaf) and spreads rapidly by leaves touching and/or by spores being blown from plant to plant by wind – so it can VERY quickly take over a whole crop. Some alliums seem to be more prone to it than others. For example while it’s spreading through our garlic crop devastatingly quickly, the clumping onions in the next row seem to be unaffected by it. So I guess we should be thankful for that.
How does it come to be?
It seems that excess moisture, both in the air and soil, plus over crowding plants are the most common causes of rust. In our own garden I initially noticed a slight discolouration on the garlic’s leaves in only one section of the patch, so I made a point to check on it closely ‘later’. However, it was two days before I got back there and by that time the rust was WELL advanced, but just in that one area. This is the region which I have referred to as the ‘mud pit’, as when the excavator created the terraces, the driver got more subsoil on top than actual top soil – bugger. As a result it’s really heavy, sticky clay in that particular spot, and this is where the garlic rust crept in. Yup, it always comes seems back to the soil.
We also planted our garlic closely – but I’ve always planted garlic closely and have never had trouble with rust before. On top of that, we had a very mild and comparatively dry winter, which is why I feel fairly confident in saying it’s probably the high clay content in our soils that ‘fueled’ it on.
Does it kill your crop?
Apparently it can kill your whole garlic crop if you just let it go and don’t try and slow it down. As far as I can tell there is no reliable way to get rid of it (naturally or chemically), but I’m really happy to be proven wrong if you know of a way? Please prove me wrong. What the rust does do is reduce the vigor of each plant it affects, meaning your garlic bulbs will be drastically smaller compared to healthy plants.
Is there ANYTHING you can do??
One blog I read (I read a lot) mentioned that if you prune the affected leaves from the plants this can slow it down and reduce the rate of it spreading, meaning you’ll still get some kind of yield from the crop. And so I gave them a pretty full-on haircut, which apparently they can cope with (fingers and toes crossed). My hope is that this will help them hang in there for at least another 4-6 weeks before I harvest them.
The ‘bald patch’ in the middle of the garlic bed is now being monitored vigorously for further signs of the dreaded rust, which sadly there are.
The healthier sections of the garlic bed are being closely watched with a hint of paranoia thrown in for good measure. I’m going through the patch daily and removing leaves here and there, hoping that this will help the crop hang in there long enough to get a decent yield. But honestly, I have a sinking feeling in my stomach.
EDIT (Nov 2019). This season we had garlic rust again (bummer) and did further research where I found this very useful factsheet from the Australian Garlic Industry Association. It lists a number of ways to treat rust with fungicides, including with copper oxychloride (250g per 100 L of water) and lime sulphur (1L per 100 L of water). We gave our crop one spray using copper oxychloride (which we also use to prevent leaf curl on our nectarine tree) and have been impressed/relieved with how it’s slowed the spread and impact of the rust on our crop. We’ll still need to harvest it a tad early, but it’s helped significantly. Please read the factsheet for complete instructions before applying it to your own crop.
Watering: Don’t water your garlic in the evening/night as this moisture will linger overnight and allow the perfect environment for fungus to creep in – water in the morning so the plants can dry out throughout the day. You can also consider installing drip line irrigation to avoid all overhead watering. Of course if it rains at the ‘wrong time’ (in the evening) there’s not much you can do about that.
Soil: If you have heavy clay soils, you can do things like add sand (works on a smaller scale), compost, ramial woodchips and plant your garlic in mounds. However we did most of these things and still got it, so choose another area of your garden with better soil if you have it or consider container gardening for this one crop. Like I said, currently our clumping onions are doing just fine in the same location, so it seems that garlic is particularly sensitive.
Tools: When dealing with any type of plant disease it’s important to sterilise your tools/materials that came into contact with it, i.e. secateurs and a bucket in this case. Make sure you wash your hands before working in other areas of the garden and change/wash your clothes as well – just to be extra careful.
Crop Rotation: To prevent lots of different soil diseases, rotate your vegetable families each season. In terms of planting garlic in the infected garden bed in the future, I read mixed views on how long you should wait until you do so. My research and experience (with white root rot, another garlic disease) leads me to think around 7 years. Luckily we have other spaces so it’s not a death sentence for alliums in our garden… Hopefully. Our market gardening friend – Suzi, has actually made the choice to stop growing garlic due to disease issues which are so common in heavy clay soils (which she also has). I’m hoping that we don’t have to resort to this and will definitely be giving it another crack next season in a different garden bed and with improved soil and new garlic stock.
Wish us luck!