Cherry tree trunk disease or pest?

I noticed something bad on my 6 year old multi-grafted sweet cherry tree on Mazzard rootstock in Northern California. I’m not sure if it is borers, bacterial canker or some other nastiness. Can anybody help me identify this? The tree is finally getting big enough to start producing well, I would hate to lose it. I don’t think it had this problem last year.

This dark canker with surrounding yellow/orange strikes resemble symptoms of Phytophthora Root and Crown Rot.

UC Davis describes this as fatal; no treatment only some soil fumigation preventions pre-planting. Is there really nothing I can do?

Last year was a hot summer, I did water the tree every week or two trickling a hose about 3’ from the trunk for a couple hours, moving it every 30 minutes. The soil got good and dry between waterings. In retrospect, I did water the surrounding grass weekly as well using a moving “tractor” style of sprinkler. This would get the trunk wet on a weekly basis.

Edit: It looks like a phosphorous acid based fungicide (Fosphite) might be worth a try, as well as mixing some gypsum into the soil and mulching with wood. Gotta try to save this tree.

Biosafe makes something called OxiPhos, but I’ve only seen it in 2.5gal jugs for nearly $200. I think this might be phosphorous acid and hydrogen peroxide.

Any recommendations on what to use and where to buy reasonable quantities are welcome.

Applied Agri-Fos Mono- and di-potassium salts of Phosphorous Acid 45.8% 50/50 dilution with water, and Pentra-bark surfactant as a trunk spray. Hope it works, supposed to be about the only thing that has a chance. Same treatment as for Sudden Oak Death. $50.

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Please update in the future on whether this treatment worked.

Any luck saving your tree, @lifespeed? I hope so. I lost a peach to phytophthora and the cherry next to it is barely hanging on. If your treatment works, I’ll try to find some Agri-Fos (in less than gallon size)!

Hi @Lizzy,

Thanks for reminding me, I need to re-apply and probably should have done so sooner. The ugly scar from the rot has not disappeared of course, but the tree is still alive and produced well this year.

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Great news!

The cherry tree is still good 5 years later.