Any organic spray is ineffective under heavy blackspot pressure. If one were, everyone would be using it. With very few using sulfur, that speaks for its effectiveness. If I used a spray I'd probably stick with Bayer Disease Control. Reports I've heard are, if used as directed, it does a good job preventing bs.

There are roses that will be fine under your conditions. There are roses that are fine here, where the blackspot pressure is much higher. So the question is how you are going to adjust your thinking.

I'm really looking for testimonials on the effectiveness or lack thereof of sulfur against blackspot. Not really looking for a philosophical debate on rose selection.

I used only sulfur for years in a worse blackspot climate than yours. If sprayed carefully every week starting at leaf-out, and maybe at midweek after a very heavy rain, it kept most roses from defoliating or looking horrible. Typically the lower 16" would be defoliated by late season. It helped that, at that time, most of my roses needed severe spring pruning, which delays the onset of blackspot by a few weeks. When I started growing more hardy shrubs, control was less effective. Also I had poor control with some of the less vigorous and most susceptible tender roses such as 'Sexy Rexy' and 'Angel Face'. Most hybrid teas did fine.

I used 2 TB of dry micronized sulfur per gallon with enough soap to spread and stick, applied in the morning after watering. In my climate, burning of the foliage was not a problem. Our hottest days are around 92 F. Do not apply overlapping with oil or oily products.

Sulfur also controls spider mites and powdery mildew. It is cheap and safe to handle.

Exactly what MichaelG wrote. And good for you zone 4. Grow what u love.

Thanks, MichaelG, for your testimonial. I think I'll give sulfur a try. What BS spray do you use now? I'm interested in learning how the results that can be achieved with sulfur compare to those that can be achieved with something like tebuconazole or chlorothalonil. For example, on a scale of 0-10, if not spraying is a 0 and tebuconazole gets you to a 9, where does sulfur land?

Did you have to spray after light rains? Did you spray in the spring and then the fall, with a break during the hottest months of the year? How did you deal with the smell? Do you have to keep agitating the spray solution (i.e., does sulfur stay dissolved or does it sink to the bottom)?

I sprayed with Greencure religiously every week this year and it had no benefits that I could discern. Based on that, Greencure was a dud on blackspot for me. If I put in the effort, I want it to work. Sounds like sulfur may not be the dud that Greencure was.

I'd welcome anyone else who's willing to share their sulfur experiences too! Olga, I think you live in a BS zone too and recall reading that you had used sulfur. How did it work for you?

I now use tebuconazole because I got lazy. It scores 9.5 used every two weeks vs. sulfur around a 7 used every week. Sulfur worked about as well as the Ortho fungicide triforine. I think it would work for you if you are faithful.

I didn't respray sulfur after light rain. I didn't take a break in summer because it doesn't get that hot here, but I would hesitate if mid-90s is predicted. Elemental sulfur doesn't smell bad, that would be lime sulfur. Micronized sulfur doesn't settle much, but I would swirl it every five roses or so.

Michael you are so honest and unpretentious. Always give good advice.

I use sulphur, k salts, and other "safe" sprays. Kind of rotate them over the growing season. Along with picking the affected leaves, i would say the result is about a 7 also. Try to be fastidious about hygiene, etc. really work on the health of the plant. I only have 3 or 4 that are really BS prone, and on those I use the big guns....but I hate that. Kind of depends on weather, rose, location of plant, etc.

Thanks for sharing your experiences! A 7 out of 10 is magnificent! I will definitely try sulfur spray next year. I would have tried it even if it was only 5 out of 10. Anything organic to avoid complete decimation. Now if only there was such an effective organic spray for japanese beetles...

Let me remind again that you must start it at leaf-out in spring. Once there are a lot of spores splashing around, it's too late for sulfur to work. Let us know how it goes.

MichaelG, thanks for noting that. I normally see the first signs of blackspot after the first flush of bloom, in early June. Before that, the leaves are completely BS free. I don't know if it's because the nights are still cool enough in March-May or daytime temps aren't warm enough for BS to take off yet. But after the first flush, the BS starts slowly in early June, and then complete defoliation by July 4th.

To minimize work, I was thinking of starting my weekly spray regimen at Memorial Day, as soon as I notice the first one or two spotted leaves in the whole garden. Does that not make sense?

If I start at leaf out in spring, I'll be spraying an extra three months--March, April, May--when normally I never see any blackspot. Maybe the garden doesn't even need fungicide during that time?

My understanding is that if you go with the less effective sprays like sulfur, you need to spray EVERY WEEK from the beginning of the season to the end. Older gardeners (before the coming of Bayer Advanced Disease Control) used to religiously repeat that you must begin spraying at the beginning of the season.

One major reason why gardeners were happy to give up sulfur in place of Bayer is that sulfur is so labor intensive. With Bayer, I wait until after the first bloom cycle--when 1 or 2 spots are seen--and spray a couple times with Bayer (2 weeks apart). That often is enough to get my roses through a good portion of the summer. Then it gets so hot here that even blackspot can't survive. With fall cooler temps, I spray with Bayer a couple more times (2-3 weeks apart)--and that usually covers it for the year. Lot easier than spraying weekly with sulfur every week for 9 months of the year.

And no, I do not live in a low-pressure BS region. I just spray wisely and thus sparingly (and buy only disease-resistant roses). : )

Kate

Back when I had to prune severely because of winter damage, I didn't see blackspot until the onset of the first flush, five or six weeks after pruning. If that is the case in your garden, you could probably wait for the first spot, then pick that leaf and spray.

Severe pruning after winter is definitely the case here in 5b, which may be why I don't see BS until after the first flush. I think that it makes sense to try starting the weekly spray at Memorial Day, which coincides with the first flush. I would spray weekly during June, then back off to spraying only after rains in July and August, when blackspot slows down too due to baking heat, then resume weekly spray once temperatures dip down in September.

I you prefer sulphur for cost, go for it, but I have used Serenade (Bayer has a licensed version of said same) for years and it has worked very well at controlling BS applying only irregularly.

We had horrid sub-tropical weather here two summers ago and I had few problems.
I do strip all my hybrid tea roses of all leaves in the fall, and of all seen bs in summer if it shows up.

It also works great on vine plants for stopping non-insect problems.