Garlic White Rot, Anyone?

A few newly weeded, super-cute, disease-free (knock on wood) garlic plants.

I love garlic. With a harvest of just four garlic braids last year, I decided we needed to ramp up production. In fact, I set a goal of growing a year’s supply of garlic this winter. I think we’re going to fall a bit short of the mark, but I’m pleased to report that we do have one long raised bed devoted to garlic and onions.

I’ve never known much about garlic diseases, and I’ve always had healthy alliums. This past weekend, however, I overheard talk of garlic white rot. By the fearful tenor of the gardener doing the talking, I decided this might be a disease worth looking up.

I didn’t have to look far. Sclerotium cepivorum, the fungus that causes white rot, can quickly kill garlic and onion plants. First the plant’s leaves turn yellow and die back. Then the bulb begins to rot. Apparently at this stage, it’s very easy to pull up the garlic, and you’ll find telltale white fluff on the bulb. The fluff later becomes more compact, forming black pinhead-sized sclerotia.

Pinhead-sized What? 

In laymen’s terms, sclerotia are hardened fungal bodies that allow the fungus to survive tough times. For garlic white rot, this means that the fungus can live in the ground for upwards of thirty years without food, just waiting for the next garlic or onion planting to feed on. I shudder to think of waiting thirty years to grow garlic again.

Of course you don’t have to wait that long to plant again, and there are a number of treatment methods available to farmers. According to UC Davis, however, chemical treatments are necessary in order to grow alliums once soil is infected with white rot.

I’m no expert on any of this, but what I found most sobering was the thought that I could inadvertently introduce white rot through planting infected garlic sets and then be stuck with the disease for the rest of my gardening life.

Aside from planting garlic from seed, which sounds like a pain to me, there are a number of prevention and organic management options, all boasting imperfect results. For instance, it’s possible to dip cloves in hot water before planting with the hope of killing off the fungus. If your soil is already infected, you can plant bunching onions. They’ll trigger the sclerotia to germinate, but won’t allow time for new sclerotia to form before harvest.

I guess the moral of the story for those of us lucky enough to have avoided the disease thus far is to be extremely cautious about where we get our garlic sets, or to plant from seed. Planting leftover cloves from the grocery store is probably a terrible idea, given that there’s no way of knowing the garlic’s origins, let alone the condition of the soil in which it grew.

But what about planting sets from a nursery? For the past several years, we’ve purchased sets from Common Ground, a local organic nursery. I’ve also saved and replanted my own elephant garlic, since I find the sets unpalatably spendy.

I spent a few hours this morning doing some long-overdue weeding in the allium bed. So overdue in fact, that plant excavation might be a more appropriate description. So far, thankfully, my little alliums look healthy despite their gardener’s lack of attention to the threat of white rot. Whether I’ll continue planting nursery sets without further precaution next year, I haven’t yet decided. At this point, I can’t see myself planting a year’s garlic from seed, but from what little I’ve learned of white rot, I’d hate for laziness to be my folly.

Before the excavation.

After the excavation.

11 Responses to Garlic White Rot, Anyone?

  1. Great information. Since I think of garlic and onions as being impervious to pests, I also believed they would be disease- and rot-free. Is growing garlic from seed an absolute guarantee of healthy plants, or is there any way that the seeds could become contaminated before they are planted?

  2. A ratio of 1 pound of clean seed should yield at least 5 pounds of garlic bulb. To avoid white rot maybe consider selecting clean seed from this years harvest. It should take about an hour or so to break apart and separate 20 pounds of bulbs into seed which should yield 100 pounds at harvest. The security just maybe worth the effort. Cheers!

    • Thanks for peroviding such specific numbers! I generally save cloves to plant the following year, especially for elephant garlic which is so expensive to buy. Unfortunately, this year’s harvest is so pathetic (due to my dreadful weeding neglect this spring) that I don’t know how many decently sized heads I’ll get. My understanding was that to really play it safe one should save the true garlic seed–not the cloves–to plant. Do you have any experience in this realm?

      • hello Sarah,
        if you are interested in growing garlic from true seed, it has only just become “commercially” available for sale in very limited quantities from Ivan’s Garlics –
        http://ivansnewgarlics.com/Home.html
        However, before you embark on it, you may wish to read up here http://garlicseed.blogspot.co.nz/p/growing-garlic-from-true-seed.html
        Another option is to grow the bulbils from hardneck garlic which is a two – four year exercise http://goingtoseed.wordpress.com/2013/09/12/growing-garlic-from-bulbils/

        • Hi Megan–Thanks so much for weighing in on the garlic propagation question, and thanks for pointing the way to more info on growing garlic from seed. fascinating to read up on this! Have you grown garlic from seed yourself?

          So far, we have continued to save cloves from each year’s harvest to plant. This seems like a fairly safe method, so long as we stay diligent about putting aside cloves every year. That said, I would love to try growing garlic from seed.

          • hello Sarah, I have bought some seed from Dr Buddenhagen and they have been sitting in the fridge for a month or so now to trick them into thinking it’s winter (I’m in NZ so it’s summer down this way:)) and will plant the seeds shortly. This is my first attempt. Apparently it can be a challenge to get true garlic seed to germinate but will be well worth the effort as the seeds are totally disease free. I have also been growing on the bulbils from my hardneck garlic which also helps to reinvigorate my stock so long as I don’t plant them in the soil as per these instructions http://www.cog.ca/uploads/TCOG%20Articles/Growing%20garlic%20from%20bulbils.pdf
            As you may have gathered, I have truely caught the garlic growing bug – fortunately my husband enjoys eating it as much as I do!

          • Hi Megan–This is so fascinating! Thanks for sharing.I was interested to read in the article you linked to on growing garlic from bulbils that the author said garlic doesn’t produce true seed. I wonder why he said that, or if I’m missing something? Either way, I am so inspired to give bulbils and maybe true seed a try. Like you, I am also a garlic fanatic! I hope you’ll check back in and let us know how your first attempt goes. Will you be reporting your results to Paul Pospisil as part of his bulbil data project?

            We keep talking about upping our seed-saving efforts across the board, and this is another inspiration to do so. Have you caught the seed-saving bug in general, or are you most interested in garlic?

            Take care,

            Sarah

  3. hello Sarah, the author of the bulbil article is correct in that garlic doesn’t “normally” have fertile flowers and even with intervention, ie removing the bulbils, won’t reliably produce true seed. Dr Buddenhagen has been growing garlic from true seed for many years and i am hoping that his garlic seed will produce flowers without any bulbils necessitating the need to remove the same.
    I am relatively new to vegetable growing and save seeds for my own use and to swap with friends but this year is the first time that I’ve seriously got into the garlic seed:) I don’t rate my chances of being successful in obtaining true seed from my own garlics – I’m not even 100% certain of the varieties I have. Definitely a porcelain, rocambole, possibly a purple stripe, an asiatic and/or a turban and definitely a silverskin and an artichoke. We have cold winters here so the silverskin often bolts and produces a scape:)
    Although I’ve been growing garlic bulbils my record keeping is abysmal so would not have sufficiently accurate data to provide to Paul Pospisil to be of any value. In the four years or so since I started growing garlic, I have always left the scapes on my hardnecks and grown out the bulbils simply because I started with very limited stock. I have definitely noticed improved vigour of the bulbil grown bulbs and even without removing the scapes, the bulbs grow to at least 1 1/2 – 2 1/2 ” bulbs depending on the variety. I will certainly keep you posted on the progress of my seed grown garlic:) got to get it to germinate which will be my first challenge!

    • Wow, Megan! It’s becoming clear to me that I need to do some serious garlic research. I never really realized how complex the various forms of propagation are. I am definitely going to try leaving some scapes this year and harvesting bulbils. I’m excited to hear how your true seed experiment turns out. Maybe I should do my research and get my facts straight before I ask this, but why are you unsure what varieties of garlic seed you have? Is this the same seed you purchased from Dr. Buddenhagen?

  4. hello Sarah, a broadband connection and google have opened a whole new world to me:) I found your blog when I was trying to determine why some of my garlic was doing so poorly but that’s another story…
    Ted Meredith has started this discussion on the SSE Allium forum which is an excellent starting point to learn about true garlic seed
    http://forums.seedsavers.org/showthread.php?t=4392
    Dr B believes that all his tgs grown garlics fit within the rocambole group and his site has got photos on the varieties tab. I have got 4 different seeds from him and this year will be my first attempt at growing tgs. He has been growing garlic for tgs production for over ten years and hasn’t given them names per se – they are grouped and numbered.
    NZ has relatively strict controls over the importation of plant material and commercial garlic growers here have to jump through very expensive bureaucratic hoops to import planting stock and as a result, we have a very limited selection of garlic for planting, just a couple of varieties of softneck artichokes and silverskins. When I look at all the different hardnecks that you can buy in the US, I can only dream 🙂
    Very few NZ seed companies offer hardneck varieties for sale – Koanga, one of our longest established heritage seed companies offers just two rocamboles (which they insist on spelling with 3 O’s:)
    Which is all a very long winded explanation of why I don’t know what varieties of tgs or garlic in my own collection are.
    All my stock of cloned garlic has come as gifts, trades and bulbs I’ve bought to eat that I’ve liked the taste of. As I read more, I am slowing trying to identify the groups that they belong in based on clove & bulbil numbers, leaf, bulb & spathe shape, maturity date etc.
    I have a huge long list of garlic bookmarks; suppliers; blogs; forums and academic research papers:) Am seriously obsessed – sad huh??
    I also own Ted Meredith and Ron Engeland’s books!

    • I’m so glad you stumbled upon our blog and that you’ve taken the time to share so many garlic insights. Thanks for pointing me toward this forum. Interesting to hear how limited your garlic options are in NZ.

      I’m all for garden obsessions!

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