Fungicide for Rust

enoughcliches(Tropical)February 3, 2007

I recently planted a row of cannas and although I have tried my best to keep the foliage dry, some of the lower leaves have contracted a minor rust infection. After doing some homework online, I know that I have quite a few organic remedies to choose from, including baking soda, milk, sulphur, chamomile tea and neem oil. However, while some sites mention that a certain spray actually *kills* the rust fungi, others claim that it is merely a preventative, or even worse, that it doesn't work at all. Is there a definite, tried-and-proven fungicide for rust, or does it (like many things organic) depend on a lot of other individual factors?

Just to clarify things, the usual advice I see in forums is to remove all infected foliage and cut back to the ground. However, this is not a preferred alternative for me, as I live in a tropical region and hence my plants do not die back and go into dormancy during winter. Rust is also very prevalent in my climate, which is why I would prefer a fungicide over a mere preventative (so I can stop the infection in its tracks instead of constantly having to spray to prevent further spread).

Also, if all else fails, I wouldn't mind a non-organic solution if it is possible for me to apply it directly to the infected areas (e.g. with a cotton bud), without affecting the rest of the plant or hurting my garden's biological diversity. Any help appreciated, thanks.

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The advice to cut off the infected plant parts and dipose of them is to try to eliminate one source of infection from your garden, it has little or nothing to do with the plants going dormant.
The first step is to determine how, or why, this disease entered you garden. Was it through a diseased plant? On the wind? Something in the soil? Once you know where it came from you can do a better job of controlling it.
The second step is to determine if this plant disease really needs to be controlled or can your plants live with what they do have.
The third step is to control the plant pathogens that cause the problem.
The fourth step is to work on your soil so your plants will grow stronger and healthier and better able to resist these disease pathogens.
the fifth step is to review what you did to see if there is any change and what affect that had.

    Bookmark   February 3, 2007 at 6:49AM
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Thanks for the quick reply.

Yes, I realize that cutting the foliage has nothing to do with the plants going dormant. But my reasoning is that since they grow continuously in my climate, it would be a "loss" for me to cut them down, whereas in a temperate region, they would have died back and regrown the next spring anyway.

1. The source of infection is probably the wind, since canna groves are very common in this region, and I have yet to see any *without* some degree of rust. This is why I have avoided wetting the foliage, but the occasional rains are beyond my control.

2. As far as I know, the cannas manage to survive even severe rust infections due to their hardy and vigorous growth. However, the rust makes the foliage terribly wretched, and I don't see any reason to just let it be *if* there exists an effective fungicide.

3. The only thing I can think of is to avoid foliar wetting, as stated above. Any other suggestions?

4. I have been doing this religiously ever since I put them in the ground: ammending with compost, humus, using compost teas and spraying with seaweed/fish emulsion.

5. Doesn't seem to be helping so far. Or maybe it is, and the infection would be much worse had I not done the above :P

Still, my aim is to attack the fungal growth as early as possible while the plants root and build up their natural resistance.

    Bookmark   February 3, 2007 at 9:07AM
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dchall_san_antonio(8 San Antonio)

There are many layers of bacteria and fungi living on the outside of your plants. The simple proof of that is the rust fungus living on the outside of your plants. The problem is that the beneficial microbes, which usually live there and protect your plants from disease, have lost their ability to do that. They need to be revitalized. Your compost tea will help with that, but also I would spray separately with milk dissolved in water at 3 ounces per gallon of water. Spray as often as you want to. Up here we shoot for spraying every 2 weeks. Your area may appreciate it every week. The milk will provide real food for the microbes living on the plant surfaces and should restore the good health to the beneficials. Once they are healthy, they should eliminate the rust fungus for you.

    Bookmark   February 3, 2007 at 12:23PM
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Thanks for the info, dchall. That's interesting, I never thought of milk in that way before. Most gardening websites merely state that milk prevents the further reproduction of rust fungi by changing the pH levels on the leaf surface. I'm eager to try out an aerated compost tea foliar spray soon as I can get my teas aerobic, that is. Which brings me back to our other discussion about tea brewing.

    Bookmark   February 3, 2007 at 12:59PM
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give us an email and I will send you an overview of OMRI certified products for rust problems...Serendae AS (QST ( and kOCIDE 2000 (copper HCL) come to mind.

    Bookmark   February 3, 2007 at 4:00PM
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Unfortunately, ntbio, where I come from the only remotely well-known organic pest/disease control available is Yates Insecticidal Soap. Sprays based on sulphur, copper or neem oil are quite impossible to find as far as I know (and I live in the capital!). Organic gardening here is pretty much in the dark ages, you see :( Which is why I am constantly scouring the internet for remedies that I can find locally.

    Bookmark   February 3, 2007 at 10:19PM
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While I have used milk to control powdery mildew and Black Spot on roses I have not found it effective at controlling rust on Hollyhock, but I have found that Hollyhocks that get rust are growing in too rich soils.
I'ne not grown Cannas up here because the rhizomes need to be dug and stored each winter and I have no place to do that.

    Bookmark   February 4, 2007 at 7:24AM
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Compost teaqs are commonly used as fungicides as they work by exclusion...populating and producing an environment not beneficial for the unwanted pest. Teas pH is low as well...for a period of time. However, organically, the best method is ROTATION of preventative measures. There are very good OMRI certified products being labeled every year...check OMRI...or any of the competitors...Oregon Tilth etc...try a hydropopnics store...people that smoke their plants don't use chemicals and you'll find good organics there!

    Bookmark   February 5, 2007 at 6:05PM
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enart(5 ONTARIO)

I have used the following spray for several years on my Hollyhocks and roses.
1 garlic bulb
1 quart water
crush the garlic bulb, place in a pan of water. bring to boil then turn off heat.let mixture cool. Strain out garlic.Pour liquid into spray bottle and spray affected areas of plants. repeat as`necessary.

Garlic is known to fight many types of disease causing fungi, including mildew,gray mold, rust. Garlic has not only been shown to fight fungi, but it also has repellent qualities for other diseases and insects. Plant Garlic
bulbs next to your roses, and you should not have any problems with aphids.

Here is a link that might be useful: home

    Bookmark   February 8, 2007 at 12:49PM
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Hello Everyone,
Thank you so much for all your comments and suggestions.
I have my cannas on in pots on a dock right on the water (I am in Fort Lauderdale) and I have been trying to figure out what were those yllow spots all over the leafs. I have used nim oil over and over again and it has not worked. And cutting the infected leafs has not worked either. I think that I am going to change my watering habbit (morning instead of evenings) and will use all your suggestions (milk and garlic spray) one at the time of course.
Once again, thank you so much and wish me luck.

    Bookmark   April 2, 2010 at 8:19PM
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