How To End Garlic Rust In Its Tracks Before It Takes Over Your Garden

Sometimes gardening feels like an endless game of checking your plants' leaves and asking, "Is this spot harmless or not?" When it comes to growing garlic (Allium sativum), tiny white, yellow, or orange flecks up to 5 millimeters wide on stems and leaves signal trouble in the form of a fungal infection called garlic rust. If you don't intervene, they can turn into rust-colored pustules and eventually dry out parts of the plant. 

Crops including onion (Allium cepa) and leek (Allium ampeloprasum), especially those growing near affected garlic, are also at risk. Thankfully, it's possible to stop garlic rust in its tracks by cutting off and discarding the leaves that are affected, using antifungal treatments, and changing up your growing practices.

A garlic plant affected by rust will develop smaller bulbs which may be missing their papery protective skins. Although it's still safe to harvest, eat, and even plant cloves from the affected garlic plants, you'll still want to tackle the problem. Otherwise, the rust can take over the garden as wind transfers its spores from plant to plant.

As with other garden diseases, the best way to stop garlic rust is with prevention. Knowing what conditions the pathogen that causes garlic rust — Puccinia allii — thrives in can help you stay one step ahead of the fungus and protect your crop. Cool and moist weather helps garlic rust take hold. When the temperature dips to 59 degrees Fahrenheit, it's time to be on the lookout, especially if you garden in a humid climate. 

The disease is also more common when your plants are clustered together too closely, so make sure there's enough space between the stalks of your garlic or related plants to ensure air circulates well around them. Too much nitrogen in the fertilizer can also trigger garlic rust. Doing a soil test can help you understand the nutrients already in the soil and leave you with recommendations for the type of fertilizer to use. This can not only help prevent rust but also help optimize your soil to grow bigger and better garlic.

If you notice the telltale flecks or pustules on your garlic, onions, or other plants, especially if it's early in the growing season, you'll want to take steps so the disease doesn't diminish your plants' health or give you a smaller crop. Remove the leaves that have signs of rust, and discard them to slow the spread of the rust. After that, treating the crop with an anti-fungal solution can tackle lingering spores. Some gardeners have success using a diluted milk spray as a natural alternative to store-bought fungicides, but there are also preventative chemical solutions, such as azoxystrobin (Quadris), that can guard the still-unaffected stalks.

Also, rotate any crops that are susceptible to the rust — including not just onions and leeks but also wild alliums and chives (Allium schoenoprasum) — out of the area where rust took hold for two to three years. This is important to protect your next harvest, since the pathogen can survive over the winter. Rotating your vegetable garden crops is incredibly easy (and so worth it), rust or not: You can grow different crop families in their own beds and then switch up the families you grow in each one.