Milk and Rust


Garlic rust is very much on my mind at the moment.  Last year around this time it appeared on my garlic, and it just appeared on Gintoino’s garlic in Portugal.

Søren had a good suggestion last year, spraying his garlic with diluted milk, and I’ve decided to try it this year.  I’m mixing it about 1:5 with water, only because it’s most convenient to buy milk by the liter here and that’s what works well to fill my spray bottle and cover the plants.  I understand nonfat milk is the best to use, but this is a special purchase here and hard to find reasonably priced, so I’m using lowfat instead.  I’ve been doing this once a week for the last two weeks, and will keep doing it about this often or after it rains, until it seems pointless to continue.

There isn’t a practical way for me to do anything close to a scientific study here, with a control section of my garden, because once I have garlic rust anywhere it will spread quickly.

What I understand is garlic rust occurs at a time of high humidity, but not when the plants are wet.  In my own experience, I see it break out in my garden most often when the days are warm, the nights cool and the humidity is high.  Because it seems to be so tied to weather conditions, it doesn’t seem like comparing the date I got it last year with the date I get it this year is a good comparison.

Anyway, to help me figure out if the milk is helping, I would appreciate if anyone reading this who has garlic in their garden will tell me if and when they get rust this year.

Rust is primarily a European plant disease, so those of you in North America probably won’t see it.

Rust is not usually a deadly disease for garlic, but it does reduce the harvest and causes the plants to die prematurely.  Delaying the appearence is what’s really important, because an infection two weeks earlier or later can mean the difference between a more or less normal harvest or one that has to be made early.

27 thoughts on “Milk and Rust”

  1. I use a dilute spray on my squash, cucumbers, and melons to protect them against powdery mildew. In my small, completely non-scientific control group (aka my garden), I have noticed that plants that I spray regularly with dilute milk before any powdery mildew shows up stay mildew-free longer, and when they do get it, the case is much more mild than without the milk.

    I don’t have any experience with rust, but the effect may be the same.

  2. Hi Christina,

    I think this was the original logic behind trying milk. Someone corrected me the last time I explained this, but what I understand is that dilute milk has been used on curcurbits for a long time now, and no one seems to understand completely why it works but it does seem to help in exactly the way you say. The leading theory seems to be that it somehow boosts the immune system of the plant. Another possibility is it coats the leaves and somehow blocks and/or slows infection.

    Garlic rust is also a mildew like disease, a different family from powdery mildew, but not completely different. The hope is that something similar might happen with garlic rust.

    Garlic rust is mostly in Europe (I think Mike of planb says it’s also in South Africa, and I’m sure it’s other places as well), but mostly not in the US. Garlic is also not always thought of as a very important crop in Europe, and rarely grown in home gardens. This means not a lot of attention is being paid to garlic rust, and it’s very likely no one has ever tried using milk before.

    Perhaps the chances of success are small, but I think if garden bloggers don’t try no one will. I think the hardest part may really be knowing if it truly does something useful.

  3. I’ll be interested to see how you get on with this. We have had rust on our garlic for the last couple of years and any ideas to slow it down would be much appreciated!

  4. It’s interesting that you say garlic rust is mostly in Europe. My garlic was severely infected with rust this year (I’m in California). Is it a different strain of rust in Europe? Can the same strain of rust infect different types of plants? I thought that my garlic might have been infected with rust that may have infected roses that were previously grown in the same area. Garlic that I grew in a different area was not infected and the cloves that I planted came from the same bulbs as the infected plants.

    I let the infection go too long before I treated it with Neem oil. The Neem killed the rust and it stopped spreading, but it was too late and the garlic didn’t get very big. Does milk kill the rust once it has started to infect the plants or is it just a preventative? I’ve used milk to treat powdery mildew on squash plants but found that Neem is far more effective. By the way, Neem is approved for organic growers here in the States. It has very low toxicity to beneficial insects, especially if it is applied when they are not active, such as very early in the morning.

  5. Hi Michelle,

    Thanks for the comment!

    If what you have is killed or even slowed down with neem oil, I doubt it’s the same rust we have here. Not even commercial/chemical sprays are effective against rust after an infection takes place. The only option garlic farmers have here is to begin spraying before a possible infection may take place, and continue until harvest. It’s very similar in this respect to potato or tomato blight.

    Commercial preventative sprays are very toxic.

    Milk too only has the possibility to prevent or slow infection.

    Garlic rust is very specific to garlic. It’s not possible to get it from plants like roses, even leeks get a form of rust that’s unable to infect garlic.

    It’s been a year or so since I read this, and I would have to double check to make sure, but what I remember is the only two places in the US with garlic rust are central California in the area around Gilroy, and a few small areas in Oregon. Of course this could have changed a bit in the last few years, but I haven’t heard of widespread outbreaks in the US. None of the garlic growers I’m in contact with in the US have never seen rust before.

    Probably what’s more important than what you do to prevent rust are the things you don’t do. In particular garlic rust is associated with excessive nitrogen/fertilizer use, or the use of fresh animal manure. Garlic also likes a lot of organic material in the ground. Keeping your plants healthy in this way can go a long way to reducing rust problems.

  6. Hi
    Whilst searching the internet regarding rust on my garlic – I came across your website. My garlic seems to be quite badly affected but, to be honest, has only 2 – 4 growing left to do. Should I take it up now or leave it? What happens to the bulbs if left? Can it spread to onions?
    I’d be grateful for any advice as I can’t find answers in any of my books.
    I live in south West France by the way.


  7. Hi Bev,

    Sorry to hear about your garlic.

    I doubt the rust can spread to your onions, but I’m not completely sure.

    I suggest leaving the bulbs in the ground as long as possible, but of course when the plants are dead, they’re dead, and there’s no point in leaving them in the ground any longer.

    Your garlic should be normal, except if you have to harvest early it will be smaller.

    Rust does not normally infect the bulbs, only the leaves. Having said that rust does spread the longer you leave your garlic in the ground, and you should be careful to destroy the infected parts of the plants and not put them into your compost.

    You will reduce your chances of getting rust early again next year if you are careful this year not to spread it too much, and it’s best to use planting stock you are completely sure is rust free if you can get it. Also like I said above, for next year, too much nitrogen fertilizer or fresh animal manure is known to make rust worse.

  8. Thanks so much for your advice Patrick. There is no sign of rust on my onions and I have some right next to the garlic – so I think you’re right. I used chopped up leaves collected from the woods near my house as a mulch. Do you think this might have contributed to the problem? There are so many it seemed like a good idea at the time.

  9. Hi Bev,

    I don’t think there’s any problem with the leaves. Garlic rust is usually spread by the wind, and if it were to be in the ground the leaves might help prevent it being splashed up by the rain and so could help.

    I cover my garlic with straw. Using something to cover it in the winter helps a lot because the temperature can vary a lot in the winter, for example it can freeze at night but the sun can shine brightly during the day and warm the ground. While garlic can tolerate mild to very cold temperatures, it doesn’t like these changes, so covering the ground can help a lot. Of course it also helps with the weeds.

    I read a study at an American university a few years ago that said when you cover the ground, the garlic grows 10% bigger.

    Other than making sure you don’t give the garlic too much fertilizer or fresh manure, I don’t think there is much you can do about the rust. Like I mention here, I’m experimenting with milk, but I don’t really expect it to help. Mostly you just have to hope the garlic rust comes late in the season.

  10. Hi Patrick
    Thanks again. It’s interesting what you say about covering the ground. I do it mainly to conserve water but also to prevent weeds. I seem to spend most of my life either watering or weeding. I don’t mind either but water is so scarce and expensive. I wouldn’t be able to say if covering has increased the size of the bulbs yet but will bare it in mind in the future.
    I’ve pulled up a few of the bulbs and they are of reasonable size. I think I’ll follow your advice and leave the rest for a month or so.

  11. Hi Patrick, thank you for the great information. I’m going to have to do some reading on this topic. Gilroy isn’t all that far from here…

  12. Hi Patrick, now you’ve got me wondering if the Neem did stop the rust or if it had just run its course and/or weather conditions didn’t favor it any more. It will be interesting to see if it returns next year and I try the neem before the rust runs rampant. I’m also interested to see the results of your milk treatments.

    After a bit more reading, I found that garlic rust is also present in the Salinas valley, even closer to me than Gilroy…

  13. Well, it’s 2011 now and I have rust really bad. I live in southwest Oregon, about 1/2 hour from the coast. I’ve been using the dilute milk and have come to the conclusion that it needs to start being applied, like the curcubits, before one ever sees rust. Here, where it’s wet/damp for 1/2 the year, once it appears,unless pulled, your garlic out of luck. Depressing.
    Your comment on too much nitrogen/manure was a lightbulb. I followed Steve Soloman’s protocol, which is sidedressings of nitrogen rich fertilizers in Feb. and April. Though I do this every year, actually, this year I am consumed with garlic rust. i have resorted to cutting off the leaves, just leaving the stalk. Guess I’ll just see what happens. Thanks for your info and thoughts.

  14. 31/10/2011
    We too have a bad infestation of garlic rust and have never had it before.We live in Blackmans Bay in Tasmania, Australia, and have had a wet, dull winter too. We cut off some leaves three weeks ago, but the rest of the leaves are now infected. We did try the milk spray, but only once. We are not going to dig the plants yet….will leave to harvest as normal in December.

  15. Geraldene,

    I’m really sorry about your plants. I hope they come out okay in the end. I’m also sorry garlic rust has made it’s way to Tasmania.

    Thanks for letting us all know about the rust, and thanks for reminding me it’s about time to get my garlic in the ground! I hope you have a great gardening season this year.

  16. We are also in Tasmania but central north
    just walked through our garlic patch which has double bolted this year and now has rust. What a pity our bulbs are as big as oranges.Just wondering anyone’s thought about the pros and cons of using this for seed?

  17. Hi Nevil,

    Sorry about your garlic too. If the bulbs are big, that’s what’s important. The rust probably won’t affect the quality much beyond making the bulbs a little smaller, unless you leave them in the ground too long after the plants die and the skins start falling apart.

    There’s little doubt the bulbs and other plant material will have some rust spores in them, and if you use them for replanting they could be a source of infection. Letting infected plants grow will also spread the spores, which can be carried long distances in the wind.

    My experience with garlic rust is if you live in an area prone to infection, there’s little you can do to prevent it. I do live in an area with established rust and high winds. Instead of fighting the infection directly, by means of trying to insure clean planting stock, quickly destroying infected plants and using chemicals, I try to make sure the plants are otherwise as healthy as possible.

    In the end rust rarely destroys crops, and well managed it doesn’t necessarily reduce harvest very much either. It’s just a real nuisance!

  18. Hi I help at a Community garden in Nth East Tasmania, we noticed 80% of our garlic have this rust on the low 2-3 leaves of the plants. We will try the milk spray to see if this helps. Should we pull the infected leaves off? As it the beginig of august and a few months from harvest, do you think our plants will be ok? Also we where hoping to use some of the bulbs to plant for next years crop, do you think this is wise or should we gather other cloves/bulbs to plant? Thank you for all or you interesting comments and knowlege. Kel

  19. Hi Kel,

    I’m sorry about your plants.

    I just finished my harvest, so you must be 5-6 months away. It’s not good at all that your plants are infected so early. Normally when my plants get infected, it’s only a month or two before harvest, and the plants can survive that long. In your case it’s going to be a challenge.

    Since the milk is experimental, I can’t say for sure what will or won’t work, but I would guess the milk will be more effective if you start applying it before the infection. In any case, there’s no harm in trying milk now.

    You might try removing the infected leaves a little, and see if that helps. In my experience rust spreads so quickly that this isn’t very helpful.

    Without a doubt the rust spores can be carried on the cloves and bulbs, and you can infect the next year’s crop by replanting them. My experience however is rust is usually more of a regional problem, and it’s not so much an issue of a garden here or there being infected. The spores can travel long distances in the wind, and for example every year when my plants get infected, I usually hear about other infections elsewhere in the Netherlands or Europe where I live at the same time.

    In my opinion, you don’t gain very much by using planting stock free of rust, because either your plants will get it or not. You might decide to take a different approach however. Likewise, some people might advise removing infected plants from the ground in order to prevent the spread, but my experience is that in fact little is lost by letting your plants go as long as possible. You might decide differently on this too.

    Good luck with everything. I hope it works out and you still get a decent harvest.

  20. Hi Patric and thankyou for your words. I will bring your letter to the community garden group and we will make a collected decition on what to do. I will suggest we will cut off and destroy the infected leaves and spray with milk solution. Do you think that the spores of this disease will stay in the soil and hinder the succesive crops? If so what do you suggest to do to the soil to rid it of the spores. We had broad beans in before the garlic and corn in before the broad beans. I wonder if either of these plantings could of made the soil/garlic succeptable? It is so interesting finding out all about Horticulture. Thank you so much again and Ill have to let you know how our crop turns out. :) Happy gardening, Kel.

  21. Hi Kel,

    I do think the spores will probably stay in the ground, and can emerge to infect a future crop. Rotation is important for garlic, for a number of reasons. There are quite a few soil borne garlic diseases, the most important of which is probably white rot. If white rot becomes well established in the ground, it can remain for 20-30 years.

    It’s very important not to use the same ground for garlic at least within 4 years, but the longer the better. Personally I try never to reuse the same ground for garlic, and I know other growers who say the same thing. Garlic can be planted very intensively, so it’s best to plant a lot of it in a small space, and never use that space again for garlic if possible.

    As far as I know, garlic rust is specific to garlic, and no other plants can be carriers the disease. To be safe, I would avoid growing garlic on ground where alliums were recently grown, but there should be no problems with broad beans or corn.

    Mostly with garlic rust, you need to just learn to live with it. You will probably get it again most future years. There’s not very much you can do to avoid it. Most of the time it’s not very serious, and doesn’t usually kill the plants before you would harvest them anyway.

    The most important thing you can do is try to keep your garlic plants as healthy as possible. Your rotation scheme with broad beans and corn sounds like a good start to this. Avoid any high nitrogen fertilizer or animal manure, as this will stress the plants by making them grow too quickly and developing lush tops that are susceptible to rust. The most resistant varieties of garlic I’ve found are the strongest and healthiest growing ones.

    This is a little bit of the idea behind the milk. It’s a very mild foliar fertilizer, but mostly it seems to make the plants healthier and stronger, and so more resistant to rust.

    Greetings from our community garden in Amsterdam. I hope you have a nice gardening year!

  22. Hi Patrick
    As someone else in this blog mentioned, I too was researching our (my partner and I) rust problem and came across this conversation. Interesting comments, particularly from the Tasmanians as I currently live in Melbourne (Australia) and will be moving to Tasmania in a couple of years.
    Had our first rust outbreak last year but fortunately it didn’t affect the harvest greatly. We destroyed the leaves and planted in a completely different area of the garden this year, but alas the rust has returned. Seems your comments about once you have rust, you keep getting rust are correct.
    We only have a small, intensively grown plot so I may strip the soil out after harvest this time and start afresh and see if that works. I note your comments about the animal manure as well. We haven’t had a lot of top growth, but do use horse manure so may vary that as well.
    Thanks for all the comments. Very useful information. Good luck with your crop.


  23. Hi all
    I have a very small town garden in the UK Yorkshire and have grown garlic in my raised bed (3m x 2m) for the last 4/5 years. Usually in a strip Accross the bed about 18″ wide with the garlic quite close together. Plant iin late autumn whilst the soil is still warm. As soon as the shoots appear I cover with a plastic water bottle, bottom cut odd and top removed. These stay on until all frost danger has gone and significantly increased the size of bulbs and cloves. Each year I move to a different strip but obviously restricted in movement due to the tiny bed!
    This year I have had garlic rust on the entire crop by the end of May. I have cut off all the leaves but still keep seeing a bit of rust. Which I remove. I am spraying with baking powder but will now try milk. I am going away at the end of July, would not usually harvest the Garlic till mid August but am wondering now I’d I should do it before I leave?

    I guess I shall have to give it a miss next year….so disappointing..unless I grow in containers and use my garden compost…

  24. Hi Thelma,

    Thanks for the comment, and sorry to hear about your rust problems.

    Honestly, I don’t think I can give you a lot of advice here. If your plants have had rust since May, the chances of them making it to August seem kind of small. On the other hand, if before you leave the plants are still looking good, there’s no reason not to leave them until you get back.

    I think the only real risk of leaving them in the ground is the tops completely die and fall off, making the bulbs hard to find in the ground.

    If you grow the garlic in commercial compost, be sure to use a little lime. Commercial compost is usually a bit acidic, and if you grow garlic in ground that’s too acidic, you get bulbs the size of marbles.

    Have a nice trip in July!

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