Overlap of oils with sulfur

April showers bring May flowers, or scab or rust or mildew.

I bought a big back of micronized sulfur but I'm not supposed to use oils (neem, karanja, etc) within 14-21 days. Wanting to stay on track with my holistic sprays has been made impossible with this guidance.

How do you manage sulfur sprays (even if used infrequently) when surely a spring holistic spray would be needed within that 14-21 day window?

Thanks!

Joanne Patton, Squire Oaks Farm
Zone 6A, Northern Virginia

This long-standing tenet is all about russeting for which there are many riffs. I'm glad you brought this concern to the fore, Joanne, as it would be good to hear a range of actual experience in this thread.

Way back, it was noted that a petroleum-based dormant oil followed by sulfur within 30 days increased russeting. That set an impossible stage for a fledgling grower like myself in the early 90s . . . and soon I would come to question many aspects of conventional organics. Truth is sulfur alone can cause russeting. Same for fixed copper (which incidentally is applied with oil to help spread mineral particles) when used much beyond green tip. Same for copper soaps if conditions go awry. Same for "biological fats" in a straight up holistic program, primarily neem oil. Much depends on the cultivar and temperature. One thing worth pondering is how bad is a degree of russeting of fruit skin in order to check disease pressure? John Bunker of Fedco Trees has told me about studies showing that fruit brix goes up under russeting . . . thereby flipping this conversation entirely on its head.

Transition scenarios and drawn out cloudy weather can call for a mix of thoughtful approaches. Playing the sulfur card for big wetting events while at the same time keeping up plant immune function and competitive colonization with holistic sprays is a reasonable course of action in my opinion. Those health-focused apps are timed ideally to boost phytochemistry while the sun still shines (a day if not two before grayer weather moves in). Now say a rainy period begins. Are you trying to use sulfur proactively as well, before the leaves get wet? Or are you timing the allopathic app to acidify moisture puddles on the leaf midway? Who's done what? And most importantly, how was the fruit finish come harvest?

Lost Nation Orchard
Zone 4b in New Hampshire



Edited 1 time(s). Last edit at 04/05/2017 04:43PM by Michael Phillips.

So, if I'm understanding this the prohibition on overlapping oils and sulfur is primarily about cosmetic damage to the fruit?

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania

Applying sulfur and oils within 7 days of each other may lead to fruit russetting, but more importantly it can lead to foliar tissue damage. However, will it decimate your trees or your crop? The answer is: it depends on the timing. As we know, lime sulfur (calcium polysufide and oil) is an effective blossom thinner because it is caustic and burns the petals when used appropriately. It also reduces Pn and can affect tree growth and fruit development - and this is how it thins fruit after fruit set. I suppose at high enough rates under the wrong conditions (e.g., very hot) it could defoliate a tree. I never seen it, but I am also very cautious about using sulfur and oil close together. At dormant or delayed dormant or even silver tip, I suppose oil and sulfur applied together or in close timing is theoretically safe, but not something I would recommend. So, if applied together or in close temporal proximity or near frosts/freezes, sulfur and oil can cause problems from unintended fruit thinning, blossom thinning, foliar burn, defoliation, and even tree death. But used properly and with appropriate cautions, there shouldn't be any issues at all. These are not recommendations, shouldn't be considered strong suggestions or even hints without professional assessment of YOUR conditions which requires a site visit or personal conversation.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Last week I did a holistic spray, which included .5% neem. The next day I sprayed micronized sulfur. 10lbs per 100 gallons. I decided to gamble on it because we were about to get a huge rain and I knew I wouldn't be able to get sulfur on after the rain. The trees were between 1/2" green and pink. It was cool--high forties/low fifties. Partly sunny.
It's now four days since I sprayed the sulfur and there is no apparent foliar damage on any of the varieties yet. The varieties showing significant green were: Hewes Crab, Golden Russet, Ashmead's Kernel, Harrison and Domaine.
I'll post if I see any damage within the next few days.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania

This is very interesting and something I have wondered about. Given that neem is a seed oil and almost all precautions are for the use of petroleum or mineral oils, I guess I am not all that surprised with your ad hoc results. As well, 0.5% is pretty low rate of oil and sulfur isn't low, but certainly not full label rate. I would be interesting to see if 1% or 2% neem plus sulfur gave similar results. Anyway, keep us updated and let us know if there are any changes or concerns.

Mike Biltonen, Know Your Roots
Zone 5b in New York

Well, I believe I get a phytotoxic response to doing sulfur one day and neem oil the next. As I mentioned in my post above, there were no immediate signs of phytotoxicity. It was only a few weeks later that things seemed off. Leaves were small and dry looking on Ashmeads and some Hewes. Similar impact on other varieties but less pronounced. I won't do that again.

Nat Bouman
Growing cider varieties in Zone 5b
On B.118 at 18X24
Susquehanna County, Pennsylvania