Why does my Japanese Maple have dry, curled leaves?

Q. The leaves on my Japanese Maple have started to turn brown and are curling at the edges. What could be causing this and what should I do?

A. There are several reasons why a Japanese Maple leaf would be dry and curled. It could be due to environmental causes, wind damage, or even high humidity (it can sometimes cause the tips and edges of Japanese Maple leaves to curl).

Dry, curling leaves can also be due to bacterial and/or fungal diseases or insect damage. For example:

• Japanese Maples can be susceptible to a disease called Verticillium Wilt, which causes leaf browning and curling (although it’s generally confined to individual branches instead of an overall browning). To control this disease, keep the tree healthy with adequate water and fertilizer. In some cases, a trunk injection with an antibiotic can be helpful since this is a bacterial disease.
• In spring, Japanese Maple leaves may be affected by a disease called Pseudomonas syringes This bacterial disease makes leaves curl and dry up as the summer progresses. The best control is to pick up all these leaves in the fall and dispose of them off-site in a sealed plastic trash bag. If this disease persists for more than a couple of years, we can spray the tree with a copper fungicide in spring as the leaves emerge.
• Mites may also infest your Japanese Maple. Mite infestations also cause the tree’s leaves to dry up and drop. Mites are very, very small and should be properly identified first before any spraying takes place. This spraying may require starting in early spring to reduce the mite’s population.

It can be tough to diagnose exactly what’s affecting your Japanese Maple. If you’re unsure of the cause, give us a call and we’ll be happy to help.