Shothole Blight (Coryneum Blight) - remove leaves or spray/drench enough?

[badatusernames]

I have a couple of plants that look to have shothole blight - one thing I can't determine is if I need to remove the leaves and destroy them, or if a root drench and spectracide foliar spray will be sufficient.

Does anyone have experience?

 

[badatusernames]

Attaching some photos

 

[shinmai]

I have a Japanese flowering apricot that I’ve had for five years or so. Three times it’s had shothole. Apricots are notoriously susceptible to every fungus or blight known to man. I live close to Lake Michigan, and the humidity makes it an ideal environment for fungus, etc.
Each time, I have defoliated completely, and removed and replaced the top inch of soil. Then I’ve sprayed with fungicide. It’s like an every other year thing for me. The tree continues to thrive, though.
One word to the wise: Beware of spraying fungicide when temperatures go above 70 degrees. They become phytotoxic, especially anything containing copper. The corpses of three black cherries can bear witness to my learning experience—one of them would have otherwise been a magnificent shohin someday.

 

[badatusernames]

I have a Japanese flowering apricot that I’ve had for five years or so. Three times it’s had shothole. Apricots are notoriously susceptible to every fungus or blight known to man. I live close to Lake Michigan, and the humidity makes it an ideal environment for fungus, etc.
Each time, I have defoliated completely, and removed and replaced the top inch of soil. Then I’ve sprayed with fungicide. It’s like an every other year thing for me. The tree continues to thrive, though.
One word to the wise: Beware of spraying fungicide when temperatures go above 70 degrees. They become phytotoxic, especially anything containing copper. The corpses of three black cherries can bear witness to my learning experience—one of them would have otherwise been a magnificent shohin someday.

Super helpful, thank you

 

[badatusernames]

I have a Japanese flowering apricot that I’ve had for five years or so. Three times it’s had shothole. Apricots are notoriously susceptible to every fungus or blight known to man. I live close to Lake Michigan, and the humidity makes it an ideal environment for fungus, etc.
Each time, I have defoliated completely, and removed and replaced the top inch of soil. Then I’ve sprayed with fungicide. It’s like an every other year thing for me. The tree continues to thrive, though.
One word to the wise: Beware of spraying fungicide when temperatures go above 70 degrees. They become phytotoxic, especially anything containing copper. The corpses of three black cherries can bear witness to my learning experience—one of them would have otherwise been a magnificent shohin someday.

Thought I’d circle back - have you ever had to defoliate your ume twice in one year? We apparently live in a rain forest now and it’s back >:0

It’s well above 70 now so thanks for the heads up. I put some infuse granular on today and will be rooting around for info before going for a full defoliation.

I heard malathion is good for it too, but I’m not sure if that changes the 70 degree equation…

 

[badatusernames]

Actually you know what

I forgot your warning about it becoming phytotoxic above a certain temperature and had sprayed with Phyton a week ago

I wonder if that’s what’s causing these leaf spots rather than the blight

 

[shinmai]

Sorry to be slow in getting back to you. Work has been onerous the last few weeks and I’ve been way from the site for a few days. I would avoid Malathion because it kills micorhyzae, and is also harmful to pollinators. There are numerous organic anti-fungals available.
My apricot developed shothole yet again three weeks ago. I cut off all the affected leaves, applied a systemic, and sprayed the entire tree. I was reminded that the biggest contributor is getting the leaves wet when watering—the spores over-winter in the bud/trunk crotch and get activated when doing indiscriminate foliar watering. Since most of my collection is azaleas, I was doing a lot of afternoon foliar watering to cool things down, and that was great for everything except the apricot and the flowering almond.
When you treat the tree, it’s also a good idea to treat the soil. I like to take OTC Walgreens 3% hydrogen peroxide, dilute it by half, and dunk the potted tree [above the soil line] for thirty seconds.

 

[badatusernames]

Sorry to be slow in getting back to you. Work has been onerous the last few weeks and I’ve been way from the site for a few days. I would avoid Malathion because it kills micorhyzae, and is also harmful to pollinators. There are numerous organic anti-fungals available.
My apricot developed shothole yet again three weeks ago. I cut off all the affected leaves, applied a systemic, and sprayed the entire tree. I was reminded that the biggest contributor is getting the leaves wet when watering—the spores over-winter in the bud/trunk crotch and get activated when doing indiscriminate foliar watering. Since most of my collection is azaleas, I was doing a lot of afternoon foliar watering to cool things down, and that was great for everything except the apricot and the flowering almond.
When you treat the tree, it’s also a good idea to treat the soil. I like to take OTC Walgreens 3% hydrogen peroxide, dilute it by half, and dunk the potted tree [above the soil line] for thirty seconds.

That’s very helpful, thank you! It appears I was mistaken - other than a handful of leaves I removed as a precaution, it seems fine now. We’ve gotten a ridiculous amount of rain this year, so it makes sense.

I appreciate the information and tip with the peroxide! Would be curious what others you’d recommend, I like pollinators!

 

[AJL]

Have you definately confirmed its Coryneum disease? Shothole in Prunus can also be caused by bacterial diseases eg Pseudomonas and Xanthomonus spp which dont respond to fungicide treatment.
Malathion is organophosphate insecticide . Why would anyone recommend it to treat a fungal or bacterial disease? Thats totally wrong advice!!
Here is a useful source of info on shothole blight and treatments which may help .
https://pnwhandbooks.org/plantdisease/host-disease/cherry-flowering-prunus-spp-shothole-coryneum-blight#:~:text=Symptoms Lesions are initially dark,to 0.25 inch in diameter.

 

[badatusernames]

Have you definately confirmed its Coryneum disease? Shothole in Prunus can also be caused by bacterial diseases eg Pseudomonas and Xanthomonus spp which dont respond to fungicide treatment.
Malathion is organophosphate insecticide . Why would anyone recommend it to treat a fungal or bacterial disease? Thats totally wrong advice!!
Here is a useful source of info on shothole blight and treatments which may help .
https://pnwhandbooks.org/plantdisease/host-disease/cherry-flowering-prunus-spp-shothole-coryneum-blight#:~:text=Symptoms Lesions are initially dark,to 0.25 inch in diameter.

Sorry - I had meant Mancozeb.

 

[AJL]

Mancozeb -use has been banned in European Union due to its harmful side effects ;see https://chemtrust.org/news/mancozeb...ult, Mancozeb will,in food and food packaging.
Youre probably better just off picking off and binning the affected leaves!!

 

[badatusernames]

Mancozeb -use has been banned in European Union due to its harmful side effects ;see https://chemtrust.org/news/mancozeb-ban-eu/#:~:text=As a result, Mancozeb will,in food and food packaging.
Youre probably better just off picking off and binning the affected leaves!!

Thank you - yeah, I’ve mostly been following Bjorn’s advice without full knowledge of how damaging some of these chemicals are. The plan was to start with what the experts say work and then start trying to pull back as I got more comfortable with other aspects of these things.

It’s probably time to start pulling back. The US seems to be more lax about this stuff but that doesn’t mean I personally want to be frivolous with it. I’ve lost trees to fungus before and got over-sensitive to it, but I’m all ears about alternatives people suggest!

I don’t want to Silent Spring my back yard, that’s for sure.