The recommended organic spray for late blight is copper. The prices for copper are astronomical on account of copper just costs a lot right now. Last year as usual I grew my tomatoes from seeds. Hearing about late blight, I tried an experiment with straw mulch for my big tomatoes, which is one recommended response. I had my cherries in pots. My neighbor bought his tomato plants. When the blight hit, his plants all dropped dead in a period of two days. My straw-mulched plants didn't do too well, since I was not used to using a straw mulch and didn't notice they needed water as often as I would have otherwise. They did get blight eventually, but it didn't matter much, since the lack of water seriously cut into their production. The plants in pots did okay. Eventually, they did get blight, no doubt from my neighbor's plants. The one that lived longest was Matt's Wild Cherry. I decided that this year I would not grow any tomatoes, that I would buy them from areas of the country that aren't getting late blight, because I just had a feeling that the late blight would be back. Sure enough, it is in PA (I'm 15 mi from PA in NY, so it's just a matter of time). A friend of mine who grows a lot of his own food is growing Matt's Wild Cherry for tomatoes this year and foregoing the copper. Good soil? My plants had very good soil. But it's soil, not a force field. When there is that much disease around, it doesn't matter how good the soil is.

Hang on a dad-gummed minute here..... I've gotten a lot of great advice on this forum and through the collective sharing of its members, found methods that work and those that don't. I believe that most of the information came from people whose real names, credentials, and education backgrounds are concealed behind the anonymity of their forum names and I am CERTAIN that 99% of them haven't been doing tests in laboratory environments or subjecting their findings to a scientific peer review board. I have also read complete silliness here. The point is that I could claim that drenching my roses in maple syrup makes them not only delicious, but has successfully prevented chili thrips in Illinois. You can post whatever you want on the internet & if you scream "LOOK AT ME" loud enough, some people [as Kim said] will take your word as gospel. On the other end of the spectrum we have scientists who require hard facts and evidence. I believe the majority of people are somewhere in the middle of those 2 extremes. In the last year I've seen a number of common household items touted as THE best cure for Omigosh-Fungus-Nightmare-Kill-It-Now, and I guess you can try them if you want, but seriously---I know what happens when I accidentally spill some of those "cures" on items inside or outside the house and I figured the risk was not worth the untested reward. If other folks want to venture into that realm, so be it, but at least fair warning has been given.

"Rhododendrons will die in wet conditions even if phytopthora isn't present...lack of oxygen to the roots will kill them." No doubt this is a useful reminder. But it's true of most plants other than things like bald cypress. Rhododendrons are notable for an extra sensitivity to this problem, almost certainly related to pathogens. I have camellias thriving in places that aren't exactly low-lying, but are on flat ground that doesn't drain well (even though, yes, camellia enthusiasts say they need drainage too) during the torrential downpours I tend to have from July to October. It's hard to imagine rhodies doing well under similar situations. Along similar lines I noticed out west along the Pacific that rhododendrons seem less sensitive to planting aspect...not exactly growing in swales but not needing to be on high spots either. I surmise that because of the lack of conditions favoring root rot out there, they can get away with this. Their innundations occur in winter when the plants are dormant anyhow. OTOH could there be a bald cypress like rhodie? Remarkably I had a Rhododendron delavayi for breeding* whose 14"X14" pot was left in a non-draining display box during Hurricane Irene. It was concealed in some shrubbery and with the semi-disastrous conditions at my place: power out for almost 72h, cellar flooded, several large branches down, I forgot about it. It's roots were *completely* underwater for roughly 72h. Amazingly it survived the unscathed and had absolutely no top dieback! * not a long term outdoor plant here though I'm sure it would survive milder winters like the last 2. My goal is to breed a tree-like zn 7 hardy, semi-sun tolerant red rhododendron. Here at least R. arboreum/R. delavayi seems relatively sun tolerant, and in maritime climates like New Zealand they grow in full sun as specimen plants in lawns. This post was edited by davidrt28 on Sat, Nov 9, 13 at 15:30

I have used Soap Shield copper fungicide for three years with excellent results for BS on roses and powdery mildew on other plants. I stopped alternating fungicides last season, and I still had little to no black spot problems. I spray about every two weeks. Be careful not to drench the foliage too much or you'll get a buildup that dries to a bright blue -- and won't wash off. Soap Shield stains very badly. Don't get it on patio pavers, either. It does not wash off! I had to wince when I saw you mention Wilt-Pruf. I'm very responsible about following package directions, and I nearly killed every evergreen and azalea in our yard by spraying them with Wilt-Pruf last November. I will never ever buy it again, and I'd never recommend it. I'm in a plant sciences curriculum in college and one of my teachers told us to never use something that can seal off the stomata, and sure enough, that's what happened to 100-ft of yews and junipers in our yard. They look awful right now, and the arborist we use said the damage is not winter burn. So be very careful if you want to use Wilt-Pruf.