I wonder if you can advise me about my Japanese Maple that was planted in spring last year – see photo attached. Midway through the summer it began to shed its leaves. It does have buds on the tree now but it looks like there is a white scale on the branches.
There may be several issues related to the health of your Japanese maple, Acer palmatum.
The summer drop of its leaves was possibly due to a lack of consistent watering, after the spring planting, throughout the summer and into the fall. It is easy for gardeners to forget that new plantings need very regular thorough watering but it’s critical to the life of the tree.
On your photo I can’t quite see the white scale you mention. If your tree was already stressed and in a weakened state from being transplanted and then went through a period of drought, it could likely have been susceptible to an insect infestation. Both soft and hard-shelled scale should be treated early this spring (late April) before bud break, with an appropriate approved product which can be purchased from most good nurseries. You may have to re-treat but follow the product instructions carefully.
On studying your photo: your tree seems to have several smaller branches growing up around the base, which, when fully leafed out, may prevent a healthy flow of circulating air. You may wish to prune out any branches that are damaged, dead, severely affected by the scale and any others that are extraneous to your key branch design. Pruning is an art in itself and if you are unsure of how to proceed, you can consult an arborist through Landscape Ontario – see link below.
Below is their general information page about your tree, the Japanese Maple.
If you are interested in reading and learning even more, I have linked a few more websites below for your perusal. All the very best with your spring project !