That’s very good summary - I believe there is one correction though, i’ve read Mancozeb for apples has a 77 day PHI in the USA
Yes, you are right, the 66 days is for grapes). Basically, the rational was that the active ingredient ethylene dithiocabamate and its degradation product ethylene thiourea are toxic (also likely carcinogen and developmental toxin) and after 77 days in apples or 66 days in grapes the levels are below 7ppm, which was set as the threshold for concern. These are reactive molecules that react with sulfur containing side chains on all sorts of proteins, that is why you don’t see resistance. But that is also the reason that they are much more toxic than more specifically targeted fungicides like Frac11 inhibitors (Merivon, Prestine, Luna Sensations).
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But there are rootstocks with improved nutrient uptake that definitely improved fruit viability. We are in a super hot and very monsoonal climate here. With nutrient light sandy loam soil.
I counter with P.2, M111 and B.10 mostly. And inoculate with pine fine sweepings and Rhizophagus Irregularis spores. It increases nutrient uptake and definitely limits conditions that cause infections. But I use rootstock noted for better; more vascular root systems.
We do get some rots; but it is often on trees with unknown rootstocks.
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M111 is what I’ve exclusively used for apples that I grafted. I do have a few startkbro semi-dwarfs that I have no idea what rootstock they used. I like M111, it’s good for our soil here.
Are you overwintering your fungicides in a climate controlled area?
I keep the liquid formulations in a dedicated fridge, solid ones in a freezer.
I’m really sorry about your apples. I think apples are very tough to grow outside of perfect dry places like northern california and eastern washington state . In five years, I’ve only ever gotten one real apple crop (another year I got like… 5 apples… on 10+ mature trees). I finally started putting real effort into them two years ago but I find it tough to control all the pests and disease pressure.
Sadly, three group 3 fungicides (DMI - indar and immunox are in this group) are not very effective against bitter rot.
Captan is effective but needs to be applied more regularly.
I agree that some varieties are just more prone to rot than others. Scott has tested lots of varieties with low numbers of sprays and limited chemicals and his lists are a good place to start.
The other option is to start spraying more like a commercial operation.
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I pasted links to two blog posts below that I found helpful. The blog is geared toward commercial apple growers in Virginia, but there’s lots of good info in it. The blog posts are also specific to last year when bitter rot had high pressure in VA - but it sounds like your conditions now: continuous warm rain for days and days.
This blog is how I learned to spray for fire blight because they make specific spray recommendations exactly when the conditions are occurring which.
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Glomerella Leaf Spot and Fruit Rot | NC State Extension Publications
So far, I’m seeing on the Summer Banana, Golden D, Swiss Limbertwig on the foliage. I have another SB on an outparcel and the fruit has as well since it wasn’t sprayed at all. My old Williams Favorite would see it on the foliage after harvest but the fruit would be fine since it ripened early July. It seems to be an August-Sept issue here in the SE. 2024 saw a nasty Glomerella and Apple Blotch outbreak. Naked feral trees everywhere in the mountain communities as early as mid August.
The Ark Black is supposed to be very susceptible. I do see some foliage issues, but the fruit is fine.
Old Fashioned Limbertwig looks like hell 24-7.
Victoria Limbertwig is fine.
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Thank you, yes disappointing… I need to geta handle on summer rots.
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Sorry for your rot problem. There’s been a lot of good advice here.
You may want to to check out an app called MyIPM. For your phone, I got it at Play store. It’s has galleries of pictures of issues.
I like it a lot. Covers all sorts of fruits and you decide what you want it to download. Disease, insects, and some weeds.
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I’m going on my third person at Illinois University Extension office. I had no idea the University had an extention that serves my county. Pictures are now with the Horticulture Educator. I hope to hear back soon.
They also have a plant clinc with a lot of services also.
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Hope your county has a live agent. We have not had an agent in 5-6 years. Weird as we are a very Agro-forestery based county.
Yep we have a live agent she emailed me back just a little.bit ago.
**I might ask that you email me a few pictures of the tree as well as any problems you see with leaves, twigs, branches, or the trunk.**
This will give me a better idea of what I’m looking at.
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I sent my agent some more pictures. Hopefully she’ll be able to identify the suspect fungi(s) and suggest treatment(s). I sure would like to get a handle on what’s going on with our apples and pears.
I thought peaches would be hard to treat but once I identified the fungus and applied the correct fungicides they are doing well now and we harvest good clean fruit 
. I hope apples and pears become the same way peaches have become to treat.
How in the world anyone can grow fruit without some fungicides is beyond me. I know we have all kinds of funky fungi around here in southern Illinois. Maybe some members are growing fruit on the moon? Is there fruit impacting fungi on the moon?
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I believe it’s just Glomerella or Bitter rot. Slightly different but…
Early apples tend to outrun the onset of both, but the foliage still can get hammered. Cleaning up the ground is a must. My former Filipino employee informed me folks down there burn under the trees help deal with fruit tree cooties. I’ve been able to manage with just Captan for years. My last application was Captan and things are doing well where I spray. The orchard I haven’t sprayed went to hell in two weeks due to the wet and rain.
Humidity brings it on. It’s been dry in NC until the last few weeks. Near zero fungal issues, bigger apples, things were looking good until about mid July. It rained and became humid and fungal issues started raging. Apples are dry climate fruit. Heck, as dry as it’s been the fruit are the largest I’ve ever grown.
Things are getting worse by the year. There was a time when tomatoes, peppers, eggplant were no spray in NC. Not anymore.
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Oddly we get European Canker and Bitter rot mainly. Rarely scab.
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I also think it’s likely just bitter rot.
I have a leaf sweeper to remove leaves from my orchard. I chip or burn when I prune. That has definitely helped me to reduce disease pressure. Unfortunately, after that, you just have to spray regularly and if Captan isn’t cutting it you can include a non group 3 like Pristine in your spray rotation.
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Concentric rings=bitter rot
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Sure looks likes like the funk we have over here to me. I was looking at Merivon tank mixed with Captan as a base but it seems bitter rot can form resistance easily so Merivon/Captan may not be a wise choice expecually since the VT article author recommends Merivon As the last cover due to 0 day PHI.
I also read bitter rot can live up to 2 years on dead wood. I was hoping to chip a bunch of wood for mulch this fall. Still will chip just won’t use it as mulch around fruit trees.
IDK… a lot of speculation on my side. Curious what IL university extension has to say about it all.