I’m having some issues on my broadleaf trees and just took two pictures to get an opinion on what the issue might be and how to fix it. First pic is an American Hornbeam. I did find small white bugs on the underside of the leaves that I removed. I wouldn’t describe it as cottony but I’m new.
The second is a trident maple. I have not seen any of those bugs on this tree, or the others I have but I’m noticing a similar look their foliage. This tree in particular I thought was due to purchasing it too early where the leaves pushed out and it had to spend a good month in a tiny greenhouse this spring. The leaves issue started early in the season so I thought it was due to being in the greenhouse at a not ideal time and its leaves suffered but now I’m seeing something similar in other trees - I’m not really sure.
To me it just looks like older, sun baked leaves rather than a major issue, but it is hard to say for sure. Water as needed and avoid keeping them too wet.
Could just be the time of the year and summer heat. easier to understand your weather if you gave us what these trees are subject to and whether you use shade cloth or not. Marty may be right. the white cottony things sound like wooly aphids. bad news. just learned to hit them with 70% isopropanol which is not toxic like regular pest control and seems to work. if wooly aphids you want to treat soon and thoroughly as they hang out in little cracks, etc. apparently are not keen to die!
Thank you for the tip! It has been warm, high 80’s with high dew points as well 70-75. I hang 30% shade cloth about 3 feet above the apex of the trees when ambient temperatures go above 85. They go into shade around 4pm due to large cedar trees to the west.
could be a little fungus because the leaves are staying wet at night. fungus loves condensed moisture and darkness. decidous are tough to keep leaves looking great this late into the season. my ume look similar to what you are showing me but my hornbeam and tridents are fine. I am having the high calcium water issue with trident getting bright orange leaves at second growth. I have been tossing epsom salts on the soil surface and watering it in to switch some of the calcium to magnesium. my tridents and hornbeams are in full sun so seem to be fine. I have only been using shade cloth for the japanese maples and azaleas. I think where I live is in zone 4 now. used to be zone 3 but what I have noticed is night temps are higher and we are getting a lot of rain this year. the weather you are showing me is similar to mine. by MPLS/ST PAUL.
I know people up north are using more shade cloth. We never used to use it until the last few years. I use 30% aluminet when I use it.
