Japanese maple disease - Ask Extension
I have a japanese maple that was planted in spring 2018. In the spring of this year, it started to show dieback of leaves on some branches and black ...
Knowledgebase
Japanese maple disease #596205
Asked September 11, 2019, 9:10 PM EDT
I have a japanese maple that was planted in spring 2018. In the spring of this year, it started to show dieback of leaves on some branches and black patches on the bark. From research I'm thinking it's either verticillium wilt or pseudomonas syringae infection. Can you help me identify the problem and how I should respond? I'm unsure if I can save the tree or if it needs to be replaced entirely. Thank you!
Montgomery County Maryland
Expert Response
Hi -- This looks like a fungal canker, possibly botryosphaeria, but a lab test would be needed to confirm what is really there. In any case, the only thing you can do at this point would be to prune down below the symptomatic area to where there is healthy tissue and allow for regrowth. In this situation, unfortunately, it looks like a major portion of the plant is affected and your best bet is probably a replacement. It looks like your tree may have been planted too deeply and possibly has too much mulch around it. You should see the top of the root flare at the soil line and have mulch that is no more than 2-3" deep and kept away from the trunk. Japanese maples are shallow-rooted and finicky about their growing conditions. If they are stressed by poor conditions, then other problems (diseases) are more likely to set in. Here is an article by our plant pathologist about some of the common problems with Japanese maples and the conditions needed to grow them well.
https://marylandgrows.umd.edu/2018/08/24/japanese-maples-in-maryland-landscapes-plant-location-care-...
Christa
https://marylandgrows.umd.edu/2018/08/24/japanese-maples-in-maryland-landscapes-plant-location-care-...
Christa
Thank you for the quick response Christa. Are there any types of antifungal treatments that I could use in combination with pruning? If I replace the tree with another Japanese maple in the same location, how likely is it that the infection reappears on the new tree? Would it be advisable to replace the tree with a conifer that may not be susceptible? Thank you!
John
John
Hi - If you replace this Japanese maple with another one, it won't necessarily have the same problem. However, Japanese maples are a bit finicky about their growing conditions. They are shallow-rooted and are therefore sensitive to stressors such as drought, poor drainage, too much
moisture, temperature extremes, too much mulch, planting too deeply, soil
compaction, etc. In addition to fungal diseases, we often see problems with dieback in these plants due to unfavorable growing conditions. We don't recommend using an anti-fungal treatment.
Looking at your planting site, we wonder if a replacement tree is needed at all. If you want the roses along the wall to grow well, they will need to be in the sun, so we wouldn't necessarily recommend a tree in this situation. There are some low-growing hollies that are evergreen that could work well in this area without blocking the light to the roses.
Christa
Looking at your planting site, we wonder if a replacement tree is needed at all. If you want the roses along the wall to grow well, they will need to be in the sun, so we wouldn't necessarily recommend a tree in this situation. There are some low-growing hollies that are evergreen that could work well in this area without blocking the light to the roses.
Christa
Thank you!
You're welcome.
