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Rust on garlic leaf

Garlic pests and diseases

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Recipes to combat some garlic pests and diseases from Penny Woodward

The main problems for home grown garlic are the fungal diseases rust and fusarium, and black aphid pests.

Black onion aphids attack all alliums, so if you have chives, leeks or onions growing in your garden, then keep an eye on and treat these as well. These pesky black critters have the habit of hiding down in the overlapping leaf bases, out of the reach of predators. As soon as you see them, spray with a dilute soap solution making sure it drips down to the leave bases. Follow up the next week with a pest oil.  If there is still some sign of the aphids then repeat this.

Rust usually only appears in the month or so before the garlic is due to be harvested. It manifests as red pustules on the leaves. It’s less likely to be a problem if you water your garlic from the base using a drip system, so there is no moisture left on leaves. If it does appear you can often keep it under control and stop it spreading by spraying with bicarbonate of soda or potassium bi-carbonate spray. If this doesn’t work, then try an organically certified copper spray, like copper hydroxide.

Fusarium root rot, also known as basal rot, is almost impossible to control once you have it. You will need to remove and throw out any affected plants, and if it happens in storage, throw out the whole bulb not just the affected clove. You can always tell fusarium because of the smell of the bulb. Don’t plant back into affected soil for at least two years, and don’t save affected bulbs for replanting. If you are concerned that rust or fusarium spores may be in your bulbs, then before planting, crack the bulbs and soak cloves overnight in a potassium bicarbonate solution.


Soap spray for black aphids

Combine 1 tablespoon of a vegetable oil based soap with 1L of water. Shake well and spray over the aphid making sure it runs down into the overlapping leaves. Alternativley buy one of the proprietry brands of soap spray based on potassium salts such as Natrasoap or Nature’s Way Vegie & Herb spray.

Oli spray for black aphids

Mix together a tablespoon of vegetable based liquid soap with a cup of cooking oil. Shake well. Add 2 teaspoons to 1 cup of water, shake well again, and spray.

Bicarbonate of Soda fungal spray for rust

To 2L of water, add a drop of vegetable oil and a drop of detergent. The oil helps to make the spray stick to the leaf, the detergent makes it spread further. Then add 4 teaspoons of bicarbonate of soda. Shake well and spray on the leaves. While this won’t kill the rust, it will stop it from spreading by making the leaf surface more alkaline.

Anti-fungal soak before planting garlic cloves

If you’ve had fungal problems then it’s worth soaking your cloves just before planting. Break the bulbs apart and soak the cloves overenight (don’t do it for any longer) in 1L of water with 1 teaspoon of bicarbonate of soda. If you also add 2 teaspoons of seaweed extract this will encourage root growth, ensuring roots start growing more quickly. Then just plant as usual