Organic fungicide interactions

19 years ago

I make occasional use of several organic fungicides during the growing season. They are Safer (sulfur for rust), Remedy (potassium bicarbonate version of Cornell for powdery mildew), and Soap Shield (copper for anthracnose or botrytis). I am also seeing a little blackspot for the first time in years, as a consequence of planting some HTs. Since I am beginning to see mild disease (rust, BS, PM) on several of my roses. I would like to spray this coming weekend.

I wonder if someone could review for me the no-nos of using these. I do know that you should water deeply before using any fungicide. I know that you should not use sulfur when the temperatures are expected to go above 80 degrees F (or is it 85?). I know that you should not use copper when temperature are too cool, but I'm not sure exactly what too cool is, and whether night time temperatures are the determining threshold. And finally I know that you should not use an oil-based fungicide such as Remedy or Cornell within at least two weeks (some say three) of using sulfur, and vice versa.

Oh, yes, one more thing -- are there any of these with which you should NOT use a seaweed based foliar product?

Paula

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Comments (4)

cloudia
19 years ago
Fascinating questions, Paula. I hope to hear the answers. I've been wondering about sulfur/copper alternating. (Not that I've even opened the copper yet.)

I didn't know that about alternating oil/sulfur. I'm glad to learn that!!! I may give up on sulfur. I tried Safer, but it seems to have left a white residue on some of the leaves which did not make me happy.
Field
19 years ago
Why ask, Paula? You've pretty much got it right. The only thing I would mention is to not mix anything containing sulfur with a horticultural oil. Spraying them within two weeks of each other hasn't been mentioned and would depend on many factors. The two-weeks rule generally applies to not spraying a hoprticultural oil and a chlorothalonil product too close together in time.

Also, if you water well and then spray late in the evening, rather than early in the morning, you can spray either sulfur or oil products as long as night time temperatures stay below 85 degrees. At least, that has proven safe for me.
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summer99
19 years ago
Please, more responses!!! This is exactly the kind of information that I need. I just started growing roses a year or so ago and this spring have been using the Bayer Disease control. Everything else in my garden is basically organic and I want to get back to that...but I don't really know what I'm doing or understand the organics...

1) Copper vs. sulfur, or alternating the two?

2) And Paula, I too would like to know if I can mix foliar products like seaweed and fish emulsion. How about Wilt-Pruf? Can it be combined with copper or sulfur?

3) Does anybody have any experience with the copper soaps like Gardens Alive's Soap shield?

4) How often do you guys on organic programs spray? What is your routine, what products, how often, etc?

Sorry, to hijack your thread, Paula...hope we both get some answers!

Summer
tinamcg
18 years ago
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.