This poor tree is having such a hard time. A bit of history on the tree: Bought in spring / early summer in Alameda CA (10A - 9B) It spent the summer getting a bit baked by the afternoon sun. It was also on concrete that was painted black. This led to some leaves drying up. We had also sprayed the leaves with water, which contributed to the leaves starting to get white mildew We have a Blood Good, small Laceleaf Maple, and Dahlias that all suffered really badly from white mildew. Dahlias died and 3/4 of our maples experienced complete loss of leaves (could be that + time of year?). Coral Bark never suffered from it A beautiful orb spider was nesting in it for quite a while (arborist suggested this might indicate pests, which we never really saw any) Around maybe August, my partner trimmed ~15-20 of the newer growth branches to shape the tree a bit (used alcohol to disinfect the sheers). I tried to propagate all of the cuttings and almost every one of them died from blackening / white mildew. Only one out of maybe a dozen has yet to develop black in the bark In late October we moved it from the afternoon sun spot to where it is in the pictures, which gets morning sun and is mostly shaded by a larger tree. This past week I discovered almost the entire leafless tree was covered in what I think were carpenter ants. It was a mix of what looked like winged ants and then smaller black bugs. I sprayed it with bonide insecticidal soap I sprayed it down with my hose on jet mode to knock of dead insects and leave leaving it bare now (some dead insects remain on the branches Questions: Dealing with white mildew 1. Should I remove all of the leaves that died that also carried white mildew? 2. I only recently noticed that the branches seem to be turning black, mostly starting from the tip and moving its way down. There are some smaller branches that also seem a bit white as well. I haven't seen any blackening in the middle of the tree or on larger branches. What's the best way to deal with this and protect the health of the tree? 3. Some parts of the branches also have developed white spots. They remind me of mealybugs, which we've had on plants inside the house. 4. Would it be good to take a soft bristle tooth brush and gently rub the bark with alcohol or some anti-fungal/bacterial?
Good afternoon @Banjo and welcome to the maples forum. To me it looks as though your Shishigashira was planted too deep at the nursery. This is very common I'm afraid. So to start with I would ensure the surface roots are uncovered a little, so that no compost touches the trunk. Next I would make sure it gets good drainage, so if the large glazed pot you have placed it in doesn't have a hole at the bottom, I would ensure it does. The roots can often get literally drowned by no escape route for the water. As it's your first year with this tree, dont worry too much, as they do take a while to settle in a new environment, so some branches will be lost. It can a be a litle uneving to see, but looking at your maple, it should be ok. do remove any dead, diseased or damaged branches. this is something we maple enthusiasts have to keep an eye on regularly. re Mealy bugs, yes do ues a little diluted rubbing alcohol, I use a cotton bud. Regarding white mildew, yes pick up every leaves and destroy, there is no better way for white mildew to return next year than to leave fallen leaves. make sure you have a good watering regime. White mildew thrives in hot dry weather. Lastly, remember that maples are understory trees, so thrive in morning sun and afternoon shade.
Blackening of twigs on Japanese maples is likely to be bacterial blight. The white spots are a natural feature of your tree.
Although it looks like a stressful season for the tree, the white markings are just the natural bark colour to my eyes as well and will not be as prominent in colour as your tree ages
I waited for more savvy members to reply, but I second what Ron and Otto wrote. Bacterial blight can be contained : prune the black twigs back to where the bark is still green, then apply copper-based fungicide (now, and just before budbreak), and you're on the safe side. Nice tree !
Thank you all or the advice! I removed the leaves that had collected in and around the pot. I'm planning to cut back the twigs later. The rain is really bad right now, so I'm worried about it getting really wet and risking more rot/bacteria. I did spray some copper fungicide on it in the meantime.
