Put in preventative measures to protect your garlic crop now.
Rust is a persistent, perennial problem in Tasmanian gardens, affecting a wide range of alliums.
Planting bio-fumigants
In beds affected by rust last year, consider planting biofumigants such as mustards (Sinapis alba), which help suppress pests and soil-borne pathogens. Autumn is an ideal time to sow them, as they tolerate light frosts and establish quickly. They also double as a useful winter salad crop.
Once you’ve finished harvesting, chop and drop the plants, then lightly dig them into the soil. This green manure adds organic matter and continues to improve soil health, perfect preparation for next season’s garlic crop.
Crop rotation
If you had issues with rust on your garlic last season, the best way to prevent it from recurring is to use fresh garlic seed and avoid planting garlic in the affected bed for a year or two.
Bottom watering
Overhead watering provides rust with ideal conditions to attach to garlic leaves. Practice bottom watering as much as possible, and water plants early in the day.
Spacing
Garlic is one of those handy crops that doesn’t require much space, but if you want to stop rust from spreading through your patch, it might be worth spacing your plants out more than usual. Garlic is typically planted in rows 10-15cm apart. However, doubling the distance between plants may prevent or, at the very least, slow the spread of rust.
Host plants
Garlic rust can also affect other common plants in the allium family such as onions, leeks and chives. Try to keep these plants as far apart as possible to minimise the risk of cross-infection.
Control
When the weather begins to warm up in spring and growth ramps up, it’s important to take a look around the garden and watch for early signs of rust, especially if you want to protect your well-loved garlic crop.
Once you see signs of rust on your garlic, the disease is likely to spread quickly. You can remove affected leaves (dispose of them in the green waste or general waste bin), which may help slow the spread. If the disease becomes widespread, you may need to harvest your garlic earlier than usual. This won’t affect the quality of the crop. You can still safely eat the garlic, but you will need to source fresh seed for next season.
Sprays
Unfortunately, once you have garlic rust in your garden, there is no cure for it. You can use commercial or organic sprays as preventative measures to deter rust or as a control method to slow the spread of rust once it is present. Conventional sprays for rust, such as lime sulphur and copper oxychloride, may not be registered for use on garlic. Always read the label before spraying and consider contacting the manufacturer prior to application. Alternatively, you can use a preventative spray made from water, soap, vegetable oil and bicarbonate of soda.
Bicarb soda preventative spray for rust
2L water
1 drop detergent
1 drop vegetable oil
4 tsp bicarbonate of soda
Shake well and spray on leaves. Reapply after rain.
