hello...i have approx 15 japanese maples, all are at least 4 years old, some as old as 50 years....this year i am seeing brown spots on the leaves of some of the tree's. not holes but spots...have not seen these in the past. i have attached a photo to help with my problem..i also have checked for bugs etc...i live in eastern ohio has anyone experienced these spots.
Yes, I have : not sure what it is exactly, but I've just treated some of mine this afternoon : Since only some of the leaves were affected, I cut them off, and sprayed "bouillie bordelaise", a copper-based treatment against fungus ans somebacterial diseases. But I only have small (bonsaï) or medium-hight specimens (no more than 1.80 metre high). It's so much easier to keep diseases and pests at bay on small trees, even with organic treatments.
I have these spots in variable amounts in my collection every year and they seem to be worse on some of the red leaved dwarfs like Shaina. I have come to the 'best guess' conclusion as an expert via Google that it may be Cercospora leaf spot. I am further convinced that their appears to be no detrimental effect to the trees that exhibit leaf spot in my collection (at least in a 4 year window that i have noticed them) as I have no dieback, limb, or tree loss since noticing it. Again each year is highly variable. I have also sprayed various foliar fungicides on them and can't tell it has any effect at least in the season I have treated it. I do think it helps not to water the leaves when able and to get rid of the leaves under the tree in the winter after it has gone dormant. In short try looking up cercospora or phyllosticta leaf spot. You can always send a sample off to your local university that offers such services and get a definitive diagnosis and treatment protocol. Good luck. Justin
