Disease Control (fung-onil vs Oxidate vs Serenade)

[fastback81]

Hey Antoniette
I sowed in fall at the end of the season. I removed all plant material, raked out the beds, turned the soil and worked it, then I sowed the cover crop (rye grass and some legumes). In Spring I cut it down and turned it under before planting (I think 30 days).

I think it worked pretty well I didn't really have a problem with blight until recently and after we had 5 days of rain straight. It still wasn't as bad as last year. Also, the soil was incredibly rich after the grass clippings decomposed.

Ron

[venturabananas]

Let me preface this by saying that I probably did things all wrong, in that I didn't start spraying before seeing any fungal problems, but instead waited until it was pretty far along. And note that I'm not absolutely positive what the fungus is, but am pretty sure it's gray mold (Botrytis).

Anyway, I started with Daconil. It did nothing that I could detect, which makes sense given its mode of action -- it is a preventative that binds to the molecules on the plant that the mold spores bind to, if I understand correctly.

Tried Serenade. Useless. Did absolutely nothing. But is was great for controlling powdery mildew on my cucumbers and some other plants.

Tried Actinovate. Didn't do anything that I could detect, despite claiming effectiveness against gray mold.

Tried bleach (b54red's recipe: 1 cup per gallon). Well, it did slow down the fungus, but it also nearly killed the plants. I know it works for him, but that concentration seemed too much for my plants, in my climate. (I had a control group that I didn't spray with bleach, so I'm sure the bleach spray was the problem.)

I have used more copper than I ever wanted to. The stuff works. It is the only thing I tried that had lasting obvious effects. It still has required weekly or bi-weekly application, but it has kept the plants alive all season.

Anyway that's been my experience. I'd love to find a regimen that involves less copper and less spraying. But I am happy that I got fruit off all my plants before any succumbed to the dreaded fungal diseases that plague my, cool, humid, coastal environment.

[venturabananas]

Note that I'm not criticizing Bill's (b54red) bleach method. Just for whatever reason, it was too strong in my climate. It killed or severely damaged new healthy tissue on the plants, not just the already diseased parts. I'm guessing that's because we never have rain in summer and despite high humidity at some times of day, it can be very dry during other parts. I might try it again at a lower strength.

[RayR]

Every fungicide, whether chemical or biological should be applied as a preventative. It's a lot easier to control fungal pathogens before they are able to successfully infect plant tissue and reproduce.

[greentiger87]

Just to add, Oxidate is not just hydrogen peroxide. It's been a while since I've read the patent, but it also has peroxyacetic acid (sometimes called peracetic acid) at a rate of "no more than 5%". Peracetic acid is pretty scary stuff, which is why the safety precautions listed for Oxidate are extremely thorough. It remains very effective even at a low concentration. It's listed on the MSDS.

I can't fathom why they choose to call it hydrogen dioxide. It's truly bizarre. The only reason I can come up with is to make sure people don't think they can substitute drugstore peroxide, which seems really petty. The fact that they don't list peracetic acid as the active ingredient is more transparent, but still frustrating.

Peracetic acid is made by combining glacial acetic acid (virtually 100% acetic acid) and very concentrated hydrogen peroxide (up to 90%) in the presence of sulfuric acid as a catalyst. Mixing table vinegar (5% acetic acid) and drugstore hydrogen peroxide (3%) will not produce any significant amount of peracetic acid, and any produced will quickly decompose.

Other likely ingredients are some kind of surfactant (probably non-ionic), acetic acid (to stabilize the peracetic acid), and a chelator (like EDTA, to bind metal ions that can decompose both hydrogen peroxide and peracetic acid).

[lakelady]

Originally Posted by fastback81

Hey Antoniette
I sowed in fall at the end of the season. I removed all plant material, raked out the beds, turned the soil and worked it, then I sowed the cover crop (rye grass and some legumes). In Spring I cut it down and turned it under before planting (I think 30 days).

I think it worked pretty well I didn't really have a problem with blight until recently and after we had 5 days of rain straight. It still wasn't as bad as last year. Also, the soil was incredibly rich after the grass clippings decomposed.

Ron

Thanks Ron, I was curious in our area how that worked out so I think I'll give it a go myself

[JamesL]

Originally Posted by fastback81

James,
I may have to be the first review, I think you're right. I can't seem to find anybody with actual experience using it.

Not sure if that is just because it's cost prohibitive or what, but I do think a lot of commercial growers use it so we'll see.

Thanks for the input

Ron,
Any updates to report on your use of Oxidate?

[JamesL]

Originally Posted by greentiger87

Just to add, Oxidate is not just hydrogen peroxide. It's been a while since I've read the patent, but it also has peroxyacetic acid (sometimes called peracetic acid) at a rate of "no more than 5%". Peracetic acid is pretty scary stuff, which is why the safety precautions listed for Oxidate are extremely thorough. It remains very effective even at a low concentration. It's listed on the MSDS.

I can't fathom why they choose to call it hydrogen dioxide. It's truly bizarre. The only reason I can come up with is to make sure people don't think they can substitute drugstore peroxide, which seems really petty. The fact that they don't list peracetic acid as the active ingredient is more transparent, but still frustrating.

Peracetic acid is made by combining glacial acetic acid (virtually 100% acetic acid) and very concentrated hydrogen peroxide (up to 90%) in the presence of sulfuric acid as a catalyst. Mixing table vinegar (5% acetic acid) and drugstore hydrogen peroxide (3%) will not produce any significant amount of peracetic acid, and any produced will quickly decompose.

Other likely ingredients are some kind of surfactant (probably non-ionic), acetic acid (to stabilize the peracetic acid), and a chelator (like EDTA, to bind metal ions that can decompose both hydrogen peroxide and peracetic acid).

Greentiger,
Curious - Why would you consider peroxyacetic acid to be of greater danger than H2O2?
Been doing a fair amount of reading on H2O2, and have picked up only obliquely on peroxyacetic acid.
Both are mentioned here with respect to Early Blight.
http://www.extension.org/pages/29878...ato-production

[fastback81]

James
I'm going to start using Oxidate after we finish canning our sauce and green tomatoes. I had success with the Fung-Onil so I wanted to bring the harvest in before I started something new.

I'm going to do some experimentation next week now that the season is basically over.

Don't worry I'll report back.

Ron

[greentiger87]

My comment wasn't intended to scare anyone off Oxidate, I was just passing on what I'd learned. It also explains how it could still be useful even though the final concentration of hydrogen peroxide in the diluted product is so low.

I think peracetic acid is a greater danger for several reasons:

1) It's always going to come packaged with a very high concentration of hydrogen peroxide and acetic acid - there's no other easy way to keep it stable. The pH of the concentrate is very low.
2) It degrades into acetic acid and peroxide, meaning it can continue to oxidize and corrode even after decomposing.
3) It is not affected by catalases and peroxidases, enzymes that can protect us from the worst of the damage caused by concentrated hydrogen peroxide
4) It is more lipid soluble than hydrogen peroxide, meaning it will penetrate deeper on a macro level (past fat and oil barriers) and a micro level (through cell membranes).
5) Though it has similar oxidizing potential, it reacts much faster than than hydrogen peroxide, and even at very low concentrations. You can pour diluted hydrogen peroxide over compost and not see any immediate reaction. Do the same with dilute peracetic acid, and it will immediately react with any organic material in the vicinity.

All that said, 27% hydrogen peroxide alone would be dangerous to handle without some personal protective equipment, so concentrated Oxidate should be treated with caution regardless.

[JamesL]

GT,
Thanks for the followup. you had identified yourself as a chemist so I was hoping for a response just like this one.

Ron,
Thanks. Looking forward to it.

FYI - I did end up spraying 2 Septoria infected plants (New Big Dwarf) with a 3% solution made from the 35% food grade H2O2. Then pruned off all the infected growth. The plants were just about done producing so I would not have been concerned it they didn't make it. (and the plants survived just fine)

It worked. Septoria is gone. Now, I don't view this as anything other than an anecdotal result, as it was hardly a controlled experiment, and who knows, with the weather change, pruning and other spraying, the result could have been a combination of factors.
But I should have the opportunity to experiment with it early next season as my neighbor gets Septoria and EB at just about the beginning of every season.

I did find a couple of reviews on Oxidate on this website. Nothing to write home about.
http://www.enviroselects.com/review/...t/list/id/174/

It also gets mentioned, along with Storox, in a fair amount of university papers for organic use, but not a lot of results posted.

I had found a very recent mention here (Aug. 2012)with respect to late blight in Poughkeepsie, NY, but it doesn't appear to have been that effective.
"We have been treating the remaining tomatoes with an organically approved copper fungicide (which is supposed to prevent spores from creating new lesions) and Oxidate (a hydrogen-peroxide like substance that is supposed to kill spores), but we are rapidly coming to the conclusion that the disease has the upper hand and that we may have to take out all the tomatoes, especially since we are weeks from harvest for most of them—more time for the disease to continue to get out of control. We are likely to keep the cherry tomatoes, since they are already ripening. We will only use Oxidate on those, since that leaves no residue on the plants or fruit."
http://farmproject.org/news/2012/08/...t-and-tomatoes

[fastback81]

Yea so I wish i read this before the first time i handled it. I figured that out on my own after I took the lid off and a couple drops turned my finger white, lol...

So Green you're saying you think the Oxidate is bad to use? I'm not so sure I'm following your post well.

[greentiger87]

I've seen a lot of references to using improved hydrogen peroxide formulations as post harvest washes, mostly to avoid the safety issues and irritancy of chlorine gas or bleach (usually calcium hypochlorite).

I wish there was some data available comparing the phytoxicity of bleach to something like Oxidate. In theory, oxidate should be better at killing spores than bleach.. but we've seen great testimony as to the effectiveness of bleach. The only complaints about it seem to be that it can damage leaves. Maybe the only reason it's not used more often is that its not registered for use on crops?

I also wonder how much of that damage is due to the high pH of common bleach. For germicidal applications, *already diluted* bleach is acidified to a pH of around neutral, which makes it much more effective in killing microorganisms and spores. This isn't widely bandied around because adding an acid directly to concentrated bleach results in the production of chlorine gas, which can be deadly (as hopefully everyone has heard by now). But when the pH is around 7, you can use much less bleach for the same killing effect.. meaning less potentially phytotoxic salt residue on the leaves.

So the question is, what aspects of the bleach solution or hydrogen peroxide solution are important to controlling the plant diseases, and which of these factors causes damage to the leaves?

1) strength of the oxidizer? hydrogen peroxide and peracetic acid win here, but bleach isn't significantly behind
2) speed of the oxidizer? peracetic acid definitely wins, but bleach isn't significantly behind
3) pH of the solution? bleach solutions are normally high pH, but can be lowered to neutral. Peracetic acid solutions will be low pH. Hydrogen Peroxide solutions are usually near neutral, but can be lowered. Normal rain has a pH of about 5. Though I've only just started using bleach, I acidified it with vinegar and have yet to see any damage.
4) surfactant choice? soaps, insecticidal or dish, will be better at killing, but will also be more phytotoxic. Non-ionic surfactants are less phytotoxic.

[JamesL]

Originally Posted by greentiger87

Though I've only just started using bleach, I acidified it with vinegar and have yet to see any damage.
4) surfactant choice? soaps, insecticidal or dish, will be better at killing, but will also be more phytotoxic. Non-ionic surfactants are less phytotoxic.

GT,
What are you targeting with bleach? And at what concentration?
Adding vinegar!?!? At what ratio, and how are you protecting yourself from the obvious byproduct?

Surfactant - Molasses clearly works well with some products, but I don't know if it would have any value mixed with bleach, H202, or vinegar. Thoughts?

I have also used Saponin via a powdered form of soap nut.

[greentiger87]

Septoria leaf spot, and potentially early blight. Early blight destroyed my spring plants, though I was still able to get a great harvest. But I'm accustomed to oversummering the plants and enjoying a new crop right about now..

You can add bleach to dilute vinegar and no chlorine gas is produced. I usually dilute the vinegar first and then add the bleach. This doesn't mean that *less* chlorine gas is produced. The concentrations (really, pH in this case) actually affect which reactions happen - in this case, *no* chlorine gas is produced. We're talking 1-2 oz of vinegar per gallon, at the most. Also note, I have hard water - just trying to bring down the pH to close to neutral. When the pH is about neutral, you can use just 1 tablespoon of bleach per gallon as a very effective sanitizer.

This was common practice for germicidal applications, and still is for small scale operations like small farms, animal shelters, home brewers, etc. The danger comes when people mix undiluted table vinegar (5%) with undiluted common bleach (5-6%) - that produces the toxic fumes people are warned about.

So that you don't think I'm totally nuts, here's a reliable source that concurs:
Cleaning and Sanitizing Fresh Produce and Fresh Produce Handling Equipment, Utensils and Sales Areas

Molasses is more of a sticker no? I don't think it has any true surfactant/spreader qualities. Shouldn't be mixed with bleach - some of the organic compounds may be quickly oxidized and use up the hypochlorite.

I've always wanted to use soap nuts! We have so many of them around here, but I never get around to it. I was thinking to use it more like an insecticidal soap substitute though.