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
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