Preventing garlic rust

Posted: Monday 4 March 2013
by Adam Pasco

I’ve grown garlic successfully for years. But last summer was an exception, as the warm, wet weather provided the perfect conditions for garlic rust to thrive.

Garlic rust

I’ve grown garlic successfully for years. But last summer was an exception, as the warm, wet weather provided the perfect conditions for garlic rust to thrive. Bulbous plants infected with rust usually wither and die early, before the bulbs have time to swell. This same pathogen attacks leeks, chives, and sometimes onions. The undersides of my garlic foliage became speckled with yellow patches that burst into orange rust pustules, resulting in a poor crop that simply wouldn't store through winter.

I'm not aware of any rust-resistant garlic varieties, or of any chemical controls to treat rust (even if I wanted to use them). But this year I may try garlic variety ‘Early Purple’, as this variety has been found to show more resistance than others during a trial.

I'm aiming to grow strong garlic plants that develop quickly and mature early. I'll plant the bulbs at a slightly wider spacing than before, to improve air circulation and reduce humidity around the plants. And I'll avoid high-nitrogen fertiliser as it encourages soft, leafy shoots, which are easily infected by fungal diseases.

I'll also practice crop rotation, so my garlic, leeks and onions will not be grown in the same plot of ground as last year. I’ll need to keep a close eye on my chives, which can carry rust disease into the next growing season. If mine show signs of rust again this year, I’ll lift and dispose of them, then plant new ones elsewhere.

Several garlic varieties are available now for planting during March. Cloches or sheets of polythene can be used to warm the soil before planting outside, and then left in place to provide protection and encourage development. Alternatively, individual garlic cloves can be planted in small pots or modular trays and kept in the greenhouse or a cold frame, and planted out once well rooted and growing strongly.

It’s not just garlic that suffers in wet weather. Onions can succumb to a disease called mildew. If you’ve been troubled by this, I recommend growing a new variety for 2013, called 'Santero'. It's resistant to mildew and available as heat-treated sets, which helps ensure crops don't bolt and run to seed. It’s certainly worth a try.

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Talkback: Preventing garlic rust
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Norman Pritchard 16/03/2013 at 15:31

a couple of years ago I borrowed some stuff called Bumper which cleared up the rust on my leeks. Its probably banned now.

Adam Pasco 18/03/2013 at 12:42

No, I haven't heard of that product. Like so many garden chemicals, this one has probably been withdrawn from the market. Only a very few remain, which is why it's so important for gardeners to look for cultural ways to avoid/control problems, and choose resistant varieties where possible.

However, I'm not aware of any varieties of garlic that are resistant to garlic rust. Perhaps the weather won't be so wet this year, and the garlic will grow well. Fingers crossed!

Adam Pasco 18/03/2013 at 20:12

I've just checked, and I think Bumper is a commercial fungicide, so should not be used by amateur gardeners.

Mimi66 23/05/2014 at 09:54

Hello Adam, What do you do with the plants that have been affected (all leaves are covered with rust). Are the bulbs still edible? Could I just cut off the leaves but leave the bulbs in the ground to mature or do I have to discard the whole crop?
Thank you.