Grrr… Garlic Rust and How to Deal

Early signs of garlic rust

After a particularly rainy and dismal spring, followed by May Gray (the sometime predecessor of California’s coastal June Gloom), a small patch of my garlic plants started developing white and yellowish-orange flecks on their leaves. These flecks intensified, spread to neighboring garlic plants, and soon were infecting entire leaves, causing some to wilt and die off early. I even had this disease consume an entire plant, but luckily, it was close to harvest time and the garlic bulb survived.

Rust is a fungal disease that affects garlic, but can also invade other alliums such as leeks and onions. The spores of this relentless fungus (Puccinia allii) travel by wind, so a rust infection in one part of the garden may affect garlic (or other alliums) in another part.

Garlic rust

As the fungus spreads, the flecks become orange and black pustules, indicating a common reinfection of rust in the same season.

Garlic rust

A severe case of garlic rust, especially one that appears early in the season, can reduce bulb development or kill an entire crop outright.

Homemade remedies (with mixed results) have been posted online, but in all honesty, there’s not much an organic gardener can do once garlic rust sets in. The only way to get rid of the fungus is by snipping off the leaves as soon as you see the rust start to appear. Throw the infected leaves in the trash (not the compost bin!), wash your hands and clothes, and disinfect your shears to prevent the fungus from spreading.

Even with the infected leaves removed, the garlic stalk should continue to photosynthesize and send energy down to the bulb.

Garlic affected by rust is still edible (and tasty) and unless the infection was severe, you should get a decently sized bulb at harvest time. No need to prematurely pull your crop unless the entire plant is brown and dead. (Like dead dead, not “ready and ripe” dead.)

True story: I had a garlic that was so badly infected that I had to cut off almost all its leaves. All that remained was a healthy green stalk and a bright green mohawk, both of which hung on for the next three weeks until harvest, and I was able to yank an average-sized bulb. Whether the bulb continued to develop after its hefty haircut, I can’t be sure — but there was no harm in leaving it in the ground.

Below is a comparison of a healthy head of garlic with only a slight case of rust in the middle of spring, versus a garlic that had been heavily infected over winter. The healthy garlic is the same size or even larger than my unaffected crop, while the infected garlic is noticeably smaller. Though the stunted garlic produced fewer and smaller cloves, they were still firm and flavorful and looked no different (other than being mini-sized and rather cute — I found it perfect to toss whole into a roast).

Comparison of garlic bulb with minor rust and bulb with severe rust

You are pretty much at the mercy of the weather when it comes to garlic rust, but there are a few things you can do to try to prevent it:

  • The fungus flourishes when the weather is cool, sunlight is low, and humidity is high. If you live in this type of climate or had a very wet/gray season, avoid watering your garlic plants late in the day, and especially avoid watering the leaves if they will not have a chance to dry out before evening.
  • Grow your garlic in the sunniest spot possible, and allow enough space between plants for air to circulate among the foliage.
  • Rotate your crops and do not grow garlic in the same area where rust appeared in the previous three years on any allium crop.

Even if your crop is plagued by garlic rust this season, all is not lost — you can still use the cloves as seed garlic for next season. A study conducted by the University of California found that seed garlic taken from rust-infected plants did not cause rust in the resulting new crop. Simply choose the largest cloves from the cream o’ the crop of your properly cured and stored garlic heads, and give it another go this year!

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July 11 2011      15 comments     Linda Ly
Hierbas   Jardín

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  • matin

    Hi . i,m matin from iran. Thank you so much of your post.

  • fleurieu garlic

    thanks Betty, great post. Helpful, informative and thorough. Rust seems to come and go with damp seasons, cheers ben

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  • Stavros, Greece

    Informative and intuitive post! Well done, thank you!

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  • http://www.gardenbetty.com/ Linda Ly

    Good luck this fall!

  • Sioux_c

    Thank-you so much Garden Betty!  Your info on garlic rust is exactly what i was looking for. Practical, and well written. I will take your advice.  Confidence is high!

  • fedorukville

    This year is not my year for gardening. Bad, bad garlic rust that we had to pull them out today and some of the cloves are really rotten :(. On top of that, my potatoes have blight so they too had to be pulled. Should I blame the Vancouver BC weather? I don’t know. It is so hard to be organic, grrr.

    • http://www.gardenbetty.com/ Linda Ly

      Living on the coast, I also have difficult summer weather (misty mornings and evenings). I didn’t get garlic rust this year, but I made sure not to plant my new garlic or onions in the same beds. I’ve heard that blight will remain in the soil as well, so throw everything in the trash (plants, mulch) and leave the soil exposed so it can freeze over winter and kill the spores.

      • Bill

        Wet climates breed many fungal diseases. Try introducing good bacteria and fungi. I use Mycogrow from http://www.fungi.com because it is a wide variety of organisms, but there are other products. I put it on the cloves when I plant, and spray it on the plants later. The rust is endemic to the blackberries that grow on my neighbors fence and so I spray them too. The blackberries look great as a result. I get black spots on my apple and pear trees, and it looks like the fungus that grows on the adjacent myrtles, so I spray them too. It’s not a 100% cure but it keeps the plants healthy and it’s not a chemical.

        • Gabrielle

          Hi, I’ve only just found this, googling around for rust which I have always had on my leeks, garlic, welsh onions etc. I live in Brittany France and for the last three years we’ve had June Gloom and all that goes with it. I first looked at what the RHS (Royal Horticultural Society) had to say and its “rust occurs on nitrogen rich low potassium soils (btw comfrey is a great source of potassium so mulch with that) and that “Puccinia allii has been confirmed
          as being seed-borne, but this is not currently thought to be of any
          great significance in the spread of the disease.” Your blog is really informative and it’s interesting that the UC has found different results. I wonder what the RHS source of info is. I’ll ask!

          • http://www.gardenbetty.com/ Linda Ly

            I haven’t had any rust the last two seasons, though we’ve also had unusually dry winters and springs. Does soil have a part in it? I’m not sure, as I didn’t do anything differently to amend it.

          • Bill

            I’ll try potassium. Greensand and comfrey. The red clay soil around here is very low in potassium and calcium. The fir trees and mushrooms like it but everybody who doesn’t add calcium gets blossom end rot. Composting kitchen scraps with the garden waste helps. We have been having the same dry winters, scary because if the rainforest gets dry enough to burn then we’re in big trouble. We get a lot of late spring rain when it is warmer and the fungus loves it. But then the rain has been starting later in the fall so we can get a few extra tomatoes, figs, and lots of blackberries. I get my little girls up early on Sat morning and take them out to pick blackberries so mom can sleep in. When mom calls us in for breakfast then she takes the blackberries and makes a pie crust out of brownies and butter, pour in the blackberries, cover with marshmallows, and stick it in the oven. When the marshmallows run together its done. Eat it early in the day so they can burn off the sugar.

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