For the past 3 years I’ve had the same problem: my 13 year old paperbark maple tree looks very healthy every spring when it leafs out. Stating in about mid June, I start to see a few brown spots on the leaves and oner the next month this increases till most of the tree is affected and many of the leaves fall off. 2 yrs ago, 70 %of the leaves fell off, though it returned to full spring splendour the next 2 springs. This also happened to one of the crab apples on the opposite side of the driveway last year. I thought it might be wilt, as I’ve also lost all my clematis in the same area. The only treatment of given the tree is shovelfuls of compost several times throughout spring to late summer. One year I notice a number of tiny spider on the tree and spayed the maple with insecticidal soap. Is there anything else I should do? Do you think it’s wilt or something else? The tree receives sufficient light and water. The tree is well protected from the wind and no winter salt get on it.
The problem that you describe with your paperbark maple is most likely Verticillium wilt. While it is a fungal disease that lives in the soil, it doesn’t necessarily affect plants every year–it can lie dormant in the soil for periods of time. When the fungus germinates in the soil, it can infect the roots of a plant and spread through the tree’s vascular system, causing the plant cells in the xylem to ‘plug’ themselves; water can no longer reach the leaves which then shrivel and die. Occasionally, the branches will die back and should be removed from the tree. For a comprehensive explanation, please see Verticillium wilt.
The fact that you’ve also lost other plants in the same area seems to indicate the presence of Verticillium wilt. It is “difficult to control as it persists in the soil indefinitely” and there is “no known chemical control”. By continuing what you have instinctively been doing–making sure it has consistent moisture, especially during dry periods and adding several inches of compost to it on an annual basis–it will hopefully continue to return to its “full spring splendour” each year.