bleach spray

[loulac]

Chrisk said : You want a 0.31% final concentration of Sodium Hypochlorite.

I’m quite impressed by the precision of the dose. Out of curiosity I’d like to know how it was reached. Could we know what dosage would be ineffective and what dosage would start to burn everything? Would it work on potatoes as well ?

[ChrisK]

Yes, two decimal points is probably a bit excessive. I simply calculated the final concentration of sodium hypochlorite based on the volumes and concentrations Bill gave. Believe I posted the calculation previously


I have no idea on the range of effective vs non-effective vs phytotoxic. Maybe Bill has made some observations.

[b54red]

The precise measurements were reached through trial and error. I spent all of one season and most of the next figuring out what mix was the happy medium that I was looking for. Once I found that mix I still kept experimenting with variations according to the conditions and the diseases I was dealing with. I found some diseases required a stronger dose or more frequent spraying to be effective and I also found that different climate conditions sometimes required adjusting the spray mix. Using higher doses isn't always damaging to leaves but the likelihood increases especially if done with the sun shining. Using less than the recommended rate isn't harmful but on the other hand it is not nearly so effective against diseases. The mix that I recommended at the start of this thread is the one that I use the most because it is the most effective on the diseases yet with little chance of damaging healthy leaves. For someone using the bleach mix for the first time I think it is wise to start with a slightly lower concentration and see how the plants react. If it isn't strong enough you can keep making the mix stronger til it does the job.

I frequently use a slightly lower dose with very mild disease symptoms and just as frequently use a higher dose with heavy disease pressure or wet conditions. If you get the dose too high and you get a little leaf burn on healthy new growth the plant usually recovers in a few days. My plants have all recovered from my mistake a few days ago.

This has been the worst year for foliage diseases that I have ever experienced in nearly 40 years of growing tomatoes in this hot humid climate. As a result the bleach spray has been used more than ever this year. I have not had two days in a row with no rain in 6 weeks and the long term forecast is not looking good so it looks like the bleach spray will continue to be necessary on a regular basis.

Bill

[loulac]

B54red wrote : The precise measurements were reached through trial and error

Many thanks for writing such an informative answer. I’m sure lots of tomatovillians will appreciate having this nice brush up of their own ways of keeping their tomatoes in good conditions. I particularly appreciated your technique of modifying dosages according to growing conditions, and the fact that a strong dosage may burn some leaves but not kill the plant.

[b54red]

Originally Posted by loulac

Many thanks for writing such an informative answer. I’m sure lots of tomatovillians will appreciate having this nice brush up of their own ways of keeping their tomatoes in good conditions. I particularly appreciated your technique of modifying dosages according to growing conditions, and the fact that a strong dosage may burn some leaves but not kill the plant.

I'm pretty sure if you get the dose strong enough you can kill the plants but I haven't gone that far yet.

Bill

[kevn357]

I just want to say thanks for sharing this information. We had 16 days straight of rain and early blight was so much more advanced than normal conditions. This solution really helped me out without spending a ton on commercial fungicides. I thought all my plants would be lost but the disease slowed and adding a copper fungicide really stopped it for now after 3 dry days. It rained again tonight and I sprayed with your solution and am feeling pretty confident.

[tnpeppers]

Just to clarify...if the bleach spray happens to get onto the foliage of healthy plants; does the spray do any damage? (Using the 5 oz of '8.5% bleach' per gallon formula.) Would it be a mistake to spritz healthy plants as a preventative?

Originally Posted by b54red

I'm pretty sure if you get the dose strong enough you can kill the plants but I haven't gone that far yet.

Bill

[b54red]

Originally Posted by tnpeppers

Just to clarify...if the bleach spray happens to get onto the foliage of healthy plants; does the spray do any damage? (Using the 5 oz of '8.5% bleach' per gallon formula.) Would it be a mistake to spritz healthy plants as a preventative?

The bleach spray if mixed at the correct dosage will not hurt healthy plant growth unless sprayed in the sunshine and then you might get some minor leaf burn on some healthy leaves. I always spray all of my plants from top to bottom and the undersides of the leaves as well preferably late in the afternoon after the sun has gone down. The only leaves that are affected are the ones infected with some type of foliage disease. Remember also that just because you don't see an obvious disease symptom doesn't mean it hasn't spread further than you think. That is why I recommend spraying as soon as you see any disease symptoms and spraying the whole plant and then following up later with a fungicide for prevention.

Bill

[tnpeppers]

I sprayed a group of tomato plants in five-gallon buckets Thursday night with the bleach solution...came out Friday morning and 75% of the branches/leaves were curling up and crunchy. Most of the nicer topleaves now have tiny little black specks on them...almost looks like black pepper. The plants actually looked reasonably fine Thursday night, just some suspicious spots here and there, so I sprayed; thinking I was catching something early. Holy cow. If there was something in there; the bleach spray really brought it to the fore. The wife and I will be clipping like madmen today...we'll see what is left by day's end. New Hampshire is 'plague central' this year...time to move. :-)

[b54red]

I hope you didn't have your solution too strong; but if you had it would burn the new leaves too. I had the same problem with my plants earlier this year after it had been raining every day for three weeks and I had been unable to spray. The plants looked okay but I knew better. When it rains that much down here with our heat and humidity diseases flourish. Even my small seedlings lost a lot of leaves because they were sitting out on a table hardening off awaiting planting and were as exposed as my plants in the garden to the constant rain. After that first spray I didn't lose nearly as many leaves in my follow up sprayings because I didn't wait as long between sprayings. Many of those plants are still producing tomatoes despite having no leaves on the bottom 5 feet of the plant.

That is why I emphasize spraying early before diseases are very noticeable if conditions are right for the development and spread of foliage diseases. It is much easier to control the diseases if you treat them early and often. Waiting only delays and worsens the inevitable. I was able to apply Daconil 2 days ago but it is starting to rain again today so I will have to use the bleach again very soon. This has been the worst year for foliage diseases that I have ever seen because it has been impossible to keep a fungicide on the plants. After all the speck, spot, mold, mildew and Early Blight I hope we don't follow up with Late Blight.

Bill

[tnpeppers]

I used 5 ounces of Clorox concentrate (the 8.5% stuff) in one gallon water. I'm going to leave the plants alone to see what happens. If they die, so be it. Late blight has turned up in MA and SW NH, so that may be what is going on here. All other plants, including peppers, are fine.

[KathyDC]

Hey Bill, how do you treat for bacterial diseases? Just curious, given all the fungal problems I'm having, I expect to have to tackle that set of problems next.

Kathy

[tnpeppers]

Bill...may I ask what type of sprayer you employ in your battle against all these blights and diseases?

[greentiger87]

Some speculative questions:

1. I wonder how this compares to hydrogen peroxide, or acidified hydrogen peroxide, like ZeroTol?

2. How important is the pH and the presence of sodium hydroxide in commercial bleach? Sodium hypochlorite is a much stronger disinfectant at neutral or very slightly acidic pH. Commercial bleach solutions contain a lot of NaOH to stabilize the hypochlorite and help dissolve organic stains.

3. The obvious advantage of hydrogen peroxide is that it decomposes to water and oxygen, instead of salt. But is the amount of salt left behind too trivial to matter, especially if bleach works better?

4. Which is more phytotoxic to healthy tissue?

5. Speculating on a mechanism... sorry if I'm stating the obvious. Oxidative stress is applied on all the cells on the leaf surface. Cells damaged by pathogens allow oxidizing ions to enter, and can't detoxify the reactive oxygen species fast enough. Intact cells keep out most of the oxidizing ions and detoxify the rest. Oxidative damage triggers the hypersensitive response. The combination of outside oxidation and HR causes the plant to shed diseased tissue.

6. Which ends up being cheaper?

I've used both in the past, but stick to acidified hydrogen peroxide nowadays because of a gut feeling and the response of earthworms to bleach spray. But that may be entirely unjustified. I haven't used either in a long time.

[ChrisK]

Yes, this is exactly what I think is happening. Plus, you get some sanitizing action on healthy uninfected tissue.

Originally Posted by greentiger87

Some speculative questions:

5. Speculating on a mechanism... sorry if I'm stating the obvious. Oxidative stress is applied on all the cells on the leaf surface. Cells damaged by pathogens allow oxidizing ions to enter, and can't detoxify the reactive oxygen species fast enough. Intact cells keep out most of the oxidizing ions and detoxify the rest. Oxidative damage triggers the hypersensitive response. The combination of outside oxidation and HR causes the plant to shed diseased tissue.