Bleach solution as a dormant spray for disease control?

denninmi(8a)November 9, 2009

Has anyone ever tried using a mild bleach solution, like 10% or even 20%, as a dormant spray in late winter to try to prevent disease?

Last year, I had a LOT of dieback of twigs and smaller branches on apricots due to brown rot attacking the flowers. It was very cool and wet at the time.

Not really a substitute for a proper disease control program, obviously, but bleach is certainly powerful and also very cheap. Rather, I'm thinking of this as augmenting traditional fungicides.

I just had the thought that this might work to "clean up" some of the spores.

I wonder if this would work? Can't see it being very phytotoxic when applied before bud break -- bleach solution is pretty widely used to sterilize plants for tissue culture, I think, and I know I've gotten weak bleach solution on plants when powerwashing my siding, driveway, etc. with no lasting ill effects.

Any thoughts? Or, am I just nuts, and if this would work, would the pros already be doing it?

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myk1(5 IL)

I've heard of people using bleach as a herbicide.

10%-20% would not be a weak bleach solution. 10% is what the CDC recommends for hospitals. That's pretty much standard for killing really bad stuff.

Here is a link that might be useful: bleach as herbicide

    Bookmark   November 9, 2009 at 4:54PM
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Beeone(4 N. Wyo.)

Bleach probably wouldn't hurt you any as long as you recognize a couple considerations. If your soil is already alkaline or borderline high in salts, bleach overspray will add sodium to the ground. At the rates you would probably use I doubt it would be enough to cause any problem unless your soil was already marginal and your soil gets little water movement across or through the soil profile to carry excess salts away.

By using bleach at 10% or 20%, I assume you are talking the ratio of household bleach to water? Household bleach is around 5-6% active ingredient and diluting that to a 10:1 or 5:1 ratio probably wouldn't hurt your trees as long as they are dormant. If you are talking about 10-20% active ingredient, you'd better be wearing a respirator when you apply it and recognize that you may badly burn the branches and buds.

I would expect the bleach would help clean up undesirable micro-organisms, but many diseases will also be carried by wind/rain/dust and by insects, so you may not be able to reduce the disease reservoir by much when you spray in the dormant season.

    Bookmark   November 10, 2009 at 12:56AM
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Just to clarify, yes, I mean one part of household bleach to 10 parts water.

    Bookmark   November 10, 2009 at 5:24AM
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alan haigh

Seems like a lot less trouble just to use a proper fungicide in the first place. Over the counter, I think the stuff is called Monterey Fungus Killer that you need to absolutely control your brown rot.

Some sites are just more difficult to control BR at than others although you are correct that it can penetrate wood and survive winter there. At tough sites there are no years where BR isn't a battle. Heavy dew is all it needs.

Monterey Fungus Killer is Fenbuconazole which I use under the name Indar, its commercial formulation. A single application on July's second week (in zone 6) is often all that's needed to irradicate BR from many sites. A second spray 2 weeks later should definately do the trick most years most sites (in my climate). Orbit (Propiconazole) is about equally affective but doesn't come in a smaller quantity than what it used by commercial growers.

    Bookmark   November 10, 2009 at 6:15AM
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Bleach certainly would be cheaper than a bought fungicide! I don't have alot of experience with the bleach solution but an alternative is coffee, believe it or not! I pour coffee over my plants that have fungus problems or even aphids. Not a permanent solution, obviously, but definitely works for a few wks. A great way to use up leftover coffee!

    Bookmark   November 10, 2009 at 7:15AM
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Scott F Smith(6B/7A MD)

Hman, I think you are referring to Monterey Garden Fungi-Fighter which is propiconazole, not fenbuconazole.

Bleach would have a similar effect to peroxide which is in fact used in some spray regimens. The primary weakness of peroxide is it is a one-shot deal and there will be no residual effect. Another similar spray is phosphorous acid. My guess is there is some reason why people don't spray bleach, e.g. the downwind neighbors get really annoyed at the smell or its really bad for the lungs of the sprayer to be awash in the stuff for a long time. Or, it could be these one-shot sprays are just not worth doing in dormant season because they have no residual effect and so their effectiveness is minimal.


    Bookmark   November 10, 2009 at 8:31AM
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Well, I'll most likely test out my theory next March, just to see if it makes a difference.

To really know, I guess I should do some of my trees and not others, to see if it damages them or if it helps control disease.

As I said, not a substitute for proper fungicides, just to sort of help them along.

I remember in one of my hort classes at Moo U (Michigan State) oh so many years ago, we did some tissue culture of petunias. First step was to wash them in 20% bleach solution, which freaked me out, because I thought it would kill them. But, it didn't, and it worked.

Anyway, I guess my other inspiration for this little experiment is just seeing how effective bleach is at killing all of the little nasties that grow around the house, like the green algae that grows on the siding on the shady side of my house when its too wet, or the little black mold that tries to grow on the cement block in my basement behind the water softener where the air doesn't circulate well.

    Bookmark   November 10, 2009 at 10:35AM
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alan haigh

Scott, yup, you're the one who I heard about it from. I should stop trying to submit info like that from memory when it is brand names that I don't use myself. At 57 my capacity is shrinking. The advice is just as useful from an efficacy standpoint- they are both systemic SI's that are most likely many times more affective than the kind of solutions being suggested here.

If you're using bleach it isn't an organic solution anyway, is it? It is certainly not a non-toxic approach. How could anyone suggest that coffee would supress brown rot for a couple of weeks- that's the most the very best fungicides can do. SI's are the only thing that seem to me to have the power of actual orchard sanitization. In other words, one shot and you're done, some sites, some years.

Still, it is an interesting experiment but I suspect if it worked it would have already been discovered. Maybe not.

    Bookmark   November 10, 2009 at 12:12PM
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The prominent horticulturist of the first half of the 20th Century, MG Kains, recommended spraying the bark of dormant trees with saturated ferrous (i.e., iron) sulfate solution to kill the various tiny tree enemies in the nooks and crannies. It was probably aimed more at microorganisms such as fungal spores rather than bugs, but I am not sure. Ferrous sulfate in a crude form is sold as "copperas" in garden stores. With this crude material you have to let the impurities that would clog the nozzle settle out first, before decanting into the sprayer. (My experience with the solution is in fighting Florida betony, with limited success I might add.)

    Bookmark   November 10, 2009 at 5:06PM
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Harvestman wrote: "Still, it is an interesting experiment but I suspect if it worked it would have already been discovered. Maybe not."

Frankly, I think so, too. Since bleach is such a widely used chemical.

But, I will probably try it just to see. As Gilda Radner said once "It couldn't hurt" (well, it might, but I think the odds of that are really slim if I apply when fully dormant).

    Bookmark   November 10, 2009 at 6:50PM
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"It couldn't hurt"

A day os so ago I looked at a small, already dormant, normally out of sight, potted American persimmon all covered with scale. A can of WD-40 was handy a few yards away. We will see how it works.

    Bookmark   November 10, 2009 at 6:56PM
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Tony(Zone 5. Omaha, Nebraska)


This is how I discovered bleach would killed weeds and grass. I was washing my trash can with straight household bleach, about three days later I have noticed everything was dead by the site where I washed the trash can. From that point on I used straight household bleach to kill unwanted weeds and grass.


    Bookmark   November 11, 2009 at 11:15AM
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Tony, yeah, I think we've all done that. But, I'm going to dilute it a lot, and only apply when fully dormant. If it fries the lawn underneath a bit, no big deal, because it will be pretty winter-dead already.

Bleach doesn't kill the roots of stuff if its only sprayed on from what I've observed. Now, if you drench the soil with it, then it does nasty things, especially to worms.

    Bookmark   November 11, 2009 at 3:46PM
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I'm curious what the outcome was? My mom once used a bleach solution on a rose as a fungicide and it cleared it up. I had another friend who said the disease is not the problem it's the soil and when his roses yellowed and got brown spots he gave them bone meal and magnesium. The roses greened up and the bacteria went away. At the time I thought the disease was cured by his fertility solution but later I observed it was July when it quits raining here. Then it made much more sense to me understanding the disease thrives in moist environments He probably used that solution for 20 years and I must admit bone meal sure makes beautiful flowers and magnesium is naturally deficient here so it makes foliage green so he was at least partly correct . I use captan as my fungicide because it's inexpensive and it works.

This post was edited by ClarkinKS on Mon, Jan 27, 14 at 7:05

    Bookmark   January 26, 2014 at 8:35PM
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olpea(zone 6 KS)

" My homemade weed killer is salt, vinegar and bleach mixed together."


As an FYI for anyone reading your post. Mixing chlorine and vinegar causes a chemical reaction releasing toxic chlorine gas. Anyone choosing to mix the two should be aware of that.

    Bookmark   January 26, 2014 at 11:21PM
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Thanks Olpea great point leave the bleach out or use just bleach. I will edit my original post Olpea. Here are some links to guides for Killing weeds or this guide or use this method

This post was edited by ClarkinKS on Mon, Jan 27, 14 at 7:09

    Bookmark   January 27, 2014 at 7:01AM
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I can help!
Orbit, Tilt and Bumper are all commercial formulations of propiconazole. They are all about $25 for a quart last time I checked. Doesn't take much so better deal than messing with bleach. it is also in medicines for athletes feet. The above are available online so easy to get! One qt. will last you guys a long time.

    Bookmark   January 28, 2014 at 8:58PM
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