My recent brush with canna rust

judderwockyJuly 6, 2011

I recently bought an infected canna. I knew it was rust when I bought it, but I really liked the variety, all the others were infected, and I didn't own any other Cannas... so I took the risk and bought it diseased.

I used the following regimen for about two weeks before I finally eliminated it. I say that with my fingers crossed, I haven't seen it in a couple of weeks.

What I did is soak a lot of cornmeal in water, I allowed it to begin brewing, and I dumped this into the soil.

I then took Kefir, a fermented milk beverage (composed of 20-40 different symbiotic bacterial and yeast strains), and painted it onto the 'bad' sections of the leaf.

The next day most of the canna spots had turned brown, and seemed to be inactive, so I made up a spray diluting the kefir down, and began spraying the leaves with it every night as the sun went down.

The spray knocks out the existing rust spores, but the problem is that new ones will come back up. I guess this is from the spores they had originally dropped in all the soil around the plant, so I started spraying about a foot or so around the canna as well, on the wall behind it, the ground, the grass, etc. Just to make sure the kefir had come in contact with everything.

After the first few days, I only noticed a few spots on a single leaf each day, then every other day, and then it basically stopped. I had to be very proactive about it making sure to spray after it had rained, etc. but eventually it seemed to suppress it.

Why I think the kefir spray works. A few random guesses.

1) very acidic, it might mess with the surface chemistry of the leaf, bumping it outside of the ph range for the rust. the chemicals in kefir also are known to suppress a lot of other bacteria and fungi.

2) stimulation of plant defenses. kefir is composed of trillions of colony forming units of bacteria and yeast. none of the bacteria hurt the plant, you can spray it on a plant all day and not really hurt it, but i'm guessing the bacteria (there are 20-40 strains in kefir) or some of their by products in the kefir activate their plant defense systems.

3) the kefir bacteria might actually eat the canna fungus. kefir is a strange substance... all the bacteria have adapted to live with one another peacefully but to kill off other types of bacteria and yeast. supposedly when exposed to foreign pathogens like e coli or salmonella the bacteria and yeast in kefir will begin engaging in "chemical warfare" with one another. some of the bacteria also serve as the food source for the yeasts I believe.

also, unlike other yogurt products, kefir contains lactobacillus plantarum ( , which i believe colonizes not only the gut, but the soil. its possible that the kefir bacteria and yeasts are living on and positively affecting the soil that the canna rust is colonizing on.

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nancyd(5/Rochester, NY)

Wow, sounds like a lot of work but I commend you on your persistence. What are simpler methods to control rust?

    Bookmark   July 14, 2011 at 1:55PM
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flying_wahini1955(houston 8b)

Sounds like between the Kefir and the cornmeal that you may have the answer to my problems. You say that you painted it with full strength Kefir - then diluted it later?
Did you cut out the infected plant material first or spray around it? Did you use the cornmeal mixture just before doing the Kefir or did you wait a few days?

    Bookmark   July 14, 2011 at 3:00PM
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@nancyd ... it was definitely a lot of work to do in the first couple of days, until I figured out I could just dilute it and spray it on. this way I get to avoid the commercial fungicides, which usually contain copper, and bother me (i have some chemical sensitivities) ... so getting rid of them organically was the priority and after the first few days it was less work... i just kept the sprayer bottle around (a used windex bottle i keep around for this sort of thing) and would run out and mist them before dusk. ill do just about anything to avoid real pesticides :)


the first couple days I painted it on, cuz i honestly didn't even know it it would work.... i didn't have to cut the foliage down ... most of the little orange dots just turned brown and went inactive,

i started experimenting with the spray bottle because it was a lot faster than dabbing it on with a napkin... so i just diluted it down to the point that it would get through the sprayer nozzle.

i just used the cornmeal mixture the one time. i use cracked corn from a local feed store, and usually the little corn husks start to turn green with mold, which means that it should be working... i think as long as there is mold present it attracts the parasitic molds that can feed on a variety of i usually only do a single treatment with cornmeal
after a few days of letting the cornmeal sit in and spraying with the kefir there was a lot of new growth popping out (fast grower) and the leaves that had been infected just looked kind of burnt where the rust had been, but otherwise healthy.... every few days or so a leaf would pop out with a rust spot, and i would sometimes cut just that piece of the leaf off to speed up the process...

i think that even after you get rid of the visible rust, the spores are still hanging out in the soil, so you are basically just waiting for them to mature and pop out back on the leaves, and spraying it seemed to seemed to keep that part in check. you might be able to speed things up by cutting off the really persistent spots occasionally one seemed to take more than a single spray to make it inactive.

also don't forget to spray around the base and on the area around it.

    Bookmark   July 14, 2011 at 5:09PM
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flying_wahini1955(houston 8b)

Thanks! I will let you know my results!

    Bookmark   July 27, 2011 at 2:48PM
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Be sure to try copper spray too if it comes back. That's what I use :)

    Bookmark   December 2, 2011 at 9:12PM
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