What are the red dots or spots on my Field Maple tree leaves?
Written by Daily Fix - Published 12-Jun-2020, last updated 13-Jun-2024
I've often wondered what these red bumps on a field maple tree are. They develop each year on new leaves. So tonight, I did some research to see if I could find out what causes red dots to appear on Acer campestre (Field Maple) leaves.
What causes red growths on Field Maple trees?
It turns out they are maple bladder galls or gall mites.
They cover the upper surface of the leaves and are caused by a small mite, vasates quadripedes.
The tree produces extra cells that form the growth which encloses the mite. The mite continues to feed and lays eggs inside.
As the new mites mature they move to other leaves to repeat the process.
The leaf galls usually only cause aesthetic damage, and sometimes early leaf drop. The following spring the new leaves form and not long later the red spots reappear.
How to treat Field Maple leaf galls
Preventative treatments and fungicidal sprays may be a possible option, but if you can live with the red growths you may choose to let nature take its course.
On their website, the RHS says:
Most gall mites do not cause damage to the health of plants, control is not necessary and they are part of the biodiversity a healthy garden supports.
If it's good enough for the RHS, it's good enough for me! From experience, the tree seems to be perfectly healthy and the damage is only superficial so I've resisted any form of chemical control.