One of the suppliers in New England is offering the Yellow Jacket brand this year for growers wanting micronized sulfur. I have some questions about that. What follows is my inquiry to the supplier.

We are going to have to zero in on this micronized sulfur business just a wee bit more. I've gotten Micro Sulf in the past that came in a 30# bag. Another brand is Kumulus. Another is Thiolux. Another is Microthiol. All four have a sulfur portion of 80%. Bonide also makes a micronized formulation but I don't know its breakdown as to sulfur content, and its more homeowner sized. Yellow Jacket is the "cheap brand" that conventional-turned-organic growers usually use with far less success. It’s label reads 90% sulfur content and it's definitely a mineral formulation of wettable sulfur . Yellow Jacket labels another of its products as “micro-fine wettable sulfur” but its US registration is cancelled according to the PAN network… though yet another Yellow Jacket product called “wettable sulfur II” uses an accompanying name of “Clean Crop Microfine Sulfur”… that also has a 90% sulfur content. That formulation is not on the OMRI list for certified organic growers, according to Brian Caldwell in New York. I’m not trying to be a pain here but this word “micronized” is critical to how I keep sulfur use in the orchard to a minimum. Micronized particles get into bark crevices and have holding power through a rain. The usual wording indicating this states that "particle size is less than five microns". Mineral formulations of wettable sulfur require as many as 10X the number of applications to come anywhere near the results I've been getting with micronized sulfur in my orchard. Liquid (flowable) formulations of sulfur like THAT have a 52% sulfur content… and thus a need for seemingly higher rates. MicroFlo makes the Sulfur 6L that I used to use before the dry-flowable micronized product became available. I used the Nufilm 17 sticker with liquid sulfur back then to gain more staying power on the leaf... a spray addition I find unnecessary with the better micronized sulfur formulations.

I use a rate of 8# per acre per hundred gallons of water, which amounts to actual sulfur of slightly more than 6# per acre with a properly micronized brand. Last year I applied sulfur twice, with extreme precision as to wetting events, infection period, and ascospore maturity. Far more goes into holistic disease management of tree fruit disease, of course, but its a "sulfur baseline" to compare what we each do. I was pleased as could be with scab control in Lost Nation Orchard in 2008. I would love to be educated further about the world of sulfur. Who's using what product? At what rates? Does the percentage of active ingredient indicate the same thing to you that it does to me? What are people paying this year for micronized (or not) sulfur? Who knows? All this may drive me to finally give up the last of the sulfur habit... and rely entirely on supporting the "good guys" in a biologically-active orchard!

I use THAT sulfur as needed, but haven't been doing this long enough to have a rate dialed in. I've been following label recommendations, but may make changes as I get some more experience.

We use Microthiol and/or Thiovit, which we have been told are the best formulations available (and more expensive of course!). We use a rate of 3.5 kg/ha (about 3 pounds per acre), and usually end up spraying 10 or 12 times per season - immediately before forecast rain periods from green tip through to about 25mm fruit diameter. Rather than a few well-timed big hits, we have to put on numerous smaller hits (the continuous sulphur bath approach) because we have a long, drawn-out spring and extended period of spore release. We apply a spray volume of 500 litres/ha, using a Hardi three-point-linkage airblast sprayer. This approach generally results in very clean fruit. It seems to be easier to protect the small fruit than the expanding shoot tips - if we do get scab in the shoot tips, we can usually burn it out with 1% lime sulphur, sprayed to the point of run-off. Weather must be bright and sunny and above 27 degrees celcius for the lime sulphur to work. We hate using lime sulphur. It is probably the worst thing an organic apple grower could do to a tree.