Great post @scottfsmith such a detailed description of what you do when.
There doesn’t appear to be a Bookmark function here. I took a screen shot and saved so I can find the thread again.
One thing I don’t see here specifically is fall treatment. Since we are going into fall now, I’m wondering what should be done after leaf fall I assume.
Also I am thinking if manually removing the rest of my trees leaves after I see about 50% leaf drop. Living near the Gulf of Mexico the trees often don’t drop all of their leaves until spring bud swell.
I think I want to defoliate and clean up my yard then spray for whatever makes sense on the trees and ground.
Anyone have a good source for lime sulfur these days? I am in need of it for grape vines at a new location and plan to also use it on some other apple trees as a dormant spray. Note the soil here is alkaline and I’ve read that maybe sulfur would be a poor choice? The grapes had quite the infection last year.
I believe all the ag based lime-sulfur has been taken off the market due to insurance issues. Unless you are looking for commercial ag quantity. However lime-sulfur is still sold as a pet spray/dip in higher concentration than the old ag/garden stuff. You can buy that and calculate the proper dilution to get to the old garden spray level.
Arbico still has it but you need to call to order.
Keystone is selling on eBay as well:
The pet dip is the same concentration if I recall from past threads. It uses a different notion of concentration on the label so appears more concentrated.
Regular wettable sulfur will lower pH (it is acidic). Lime-sulfur has a high pH around 10.5 and will raise soil pH. My understanding is that both will not change soil pH long term, but will in the short term.
Alkalinity is different than pH (but related). My soil is alkaline (lots of calcium carbonate) and so it is very hard to lower pH. Low alkalinity but high pH soil you can easily lower pH.
I also read that lime-sulfur is safer for the plants than regular sulfur (which is why people add lime) - I have no idea how true or not this is and would love to find out, but can’t seem to find any sources on it.
I have a pear blister mite problem and plan to spray sulfur, but have heard from different sources that lime-sulfur is better or sulfur is better… Anyone know?
Lime sulfur is considered better for mites but I have had both work well in my orchard. These days I use lime sulfur because it also works on other things in a delayed dormant spray. Sulfur you can spray later if you didn’t hit the mites early.
So this question ties into this thread and the recent comments on lime-sulfur. I was planning on doing dormant sprays of both lime-sulfur and dormant oil-copper this spring. And I am not quite sure of which to do when. Any thoughts on the best way to apply these, which one first, delay period between, etc.
I believe Scott’s low-impact spray schedule is lime-sulfur + oil at bud swell, optionally including copper as necessary. So you should be fine to do all three as long as your tree is still dormant, no need to wait between them. This risk in combining happens only later when tender parts of the tree are exposed. Is copper - lime sulfur - oil ok to mix for dormant spray
I have a tiny beginner backyard orchard (just peach and plums, first year fruiting) at the moment in Maryland 7b and I’m trying to balance affordability/access and toxicity (low REI included) in my spraying schedule for this year. What I’ve come up with from reading everyone’s great resources is:
Delayed dormant spray:
horticultural oil
Petal drop and onwards:
Alternate sprays of fenhexamid (Elevate) and myclobutanil (Immunox/Gravex/etc.) in combination with kaolin (Surround), Regalia, spinosad, Bt, and tri-tek.
My worry is there’s not enough coverage for peach scab in this mix as myclobutanil isn’t listed for treating peach scab specifically (although I’ve seen people here say they use/recommend it). Would tri-tek + Surround give me enough coverage or does myclobutanil have coverage for peach scab despite not being listed? I’m hesitant to add sulfurs due to a pond being nearby. Also, are there any other gaps in this coverage that I’m overlooking?
Sulfur has shown to be practically non-toxic to bobwhite quail, bluegill sunfish, rainbow trout, water fleas, and mysid shrimp. It is also practically non-toxic to the honeybee.
Myclobutanil though,has been shown to be toxic,with long lasting effects,in aquatic invertebrates.
Take care when using it.
Where do people get their Indar? I’m interested in controlling brown rot on my stone fruit but $300+ is a tough buy in. Sadly nobody around me would be up for splitting it either.
Thanks Brady for the link! However I can’t find the source they’re referencing for sulfur being non-toxic. Searches across the internet and EPA’s website only turn up older documents where EPA declined to do an environmental fate assessment on sulfur due to it being naturally occurring. (1, bottom of page 7)
Regarding myclobutanil, the source cited for fish/invertebrate toxicity seems to come from a self assessment by a manufacturer for universities.(2) The details/data of this toxicity are not shared. There’s another study I could find on toxicity in zebrafish which listed about 6 mg/L as having ill effects.(3) Most studies and data, however, I cannot get access to, for example, the Encyclopedia of Toxicology which lists it as moderately toxic but showing high environmental persistence.(4) I also checked out ECOTOX but their cited sources are often their own database, so I’m having trouble trusting that.(5)
Before I go much further down this rabbit hole, I based my initial assessment of aquatic toxicity on the values listed on the International Union of Pure and Applied Chemistry website for sulfur and myclobutanil.(6)(7) I know this is a complicated subject and in my searching I’ve encountered many seemingly contradictory statements, but I’m very happy to look at any resources people like to use and are willing to share. I’m trying to make the safest call I can regarding the information available. I’m also considering hand bagging using Clemson’s bags (considering the small size of my setup) and foregoing fungicides as much as possible.
If your soils are alkaline, that means they have a pH higher than 7 (neutral). The vast majority of fruit trees and bushes prefer slightly to moderately acidic conditions (below 7 rather than above) so lime sulfur would net the opposite of the desired result without further ammendments to counteract the pH adjustment.
Having high calcium carbonate content in your soil means you likely have a high buffering capacity with respect to pH. At work we use calcium carbonate (limestone) as treatment media for acid coal mine drainage. Your assessment on low alkalinity but high pH is definitely on track. It is easier to adjust pH downward with less buffering capacity.
All that said, I’m not sure I’ve heard of elemental sulfur used as a standalone spray, every mention on the forum I remember seeing has been lime sulfur for sprays. It’s definitely possible I missed something. I’ve seen folks using elemental sulfur for adjusting blueberry bed pH Definitely a slippery slope if too much is applied.
I have seen it for an insecticide only for pear mites when sprayed in late dormant through tight cluster. Apparently you can spray it longer than lime-sulfur. It is definitely used as an organic fungicide.
From the VA commercial tree fruit spray guide:
"SULFUR. Wettable sulfurs are finely divided, elemental sulfur particles with a wetting agent added so that the sulfur can be mixed with water and remain in suspension while being applied. The most readily available forms of sulfur are dry, wettable powder (95% sulfur) and fused bentonite sulfur (30% to 81% sulfur depending upon the brand). Sulfur dusts are available and generally are more finely divided and therefore more adherent and effective than the coarser wettable powders. Flowable sulfur products are available and their advantage over wettable sulfurs include being effective at lower rates and having better retention properties. Generally, sulfur is used in apple programs for the control of apple scab and powdery mildew. For scab, dry wettable sulfur (95WP) is used at a rate of 5 lbs. per 100 gallons in early-season sprays in a protective program. It can be used during bloom without reducing fruit set significantly, however fruit russetting and yield reduction may result if it is used under high temperature conditions. However, many orchardists growing fruit for the processing market routinely use sulfur in postbloom sprays without adverse economic effects. Sulfur is also the cornerstone for early-season and summer disease control in organic orchards. Sulfur is very effective against powdery mildew and can be combined at reduced rates (3 lbs/100 gallons) with most pesticides. On stone fruits, sulfur is effective against brown rot, although not as effective as Captan or some of the newer materials. It also has good activity against peach scab, fair activity against Rhizopus rot.
Do not use any sulfur products within two weeks before or after an oil spray. Copper, sulfur, and liquid lime-sulfur should be used by growers who intend to produce fruit for the “organic” market. Growers are cautioned to be aware of the disadvantages and limitations of these materials, compared to synthetic fungicides: sulfur is incompatible with oil, it has poor residual activity, it acidifies soil when used in seasonal programs, and it is phytotoxic to fruit and foliage when used in hot weather; liquid lime-sulfur is extremely caustic and may be dangerous to apply, it may also be phytotoxic to foliage and it may reduce leaf size and yield, several consecutive applications may need to be made to effectively eradicate scab lesions; copper sprays have better residual activity than sulfur sprays and some coppers can be used to tight cluster if surface russetting of the fruit is not a problem. Only a few copper formulations are registered for application after petal fall."
Thanks for sharing! Oh the trouble organic growing can be… I’m not convinced it’s the ‘better route’ for my purposes but it’s good to have more tools in the toolbox.