The last two years this is continually and constantly occurring. The sap is like a sticky, lumpy white glue running down the trunk of two Japanese maple trees. Their height is about 8 feet with a spread of 10 feet, planted 7 years ago and 12 feet apart. The soil is well drained and never gets water logged. I live in an urban city area on a busy main road, and I have looked for more trees with this problem without success.
White Sap on the Trunk of Japanese Maple Trees
Certified GKH Gardening Expert
There are two things that it may be.
The first is that the tree has borers and the sap is leaking from the borer damage. This article will help you with that:
The other is that the tree has Japanese Maple Scale. The sap would actually not be sap, but honeydew secreted from the scale bugs. The lumpy white appearance is the scale itself, which is a bug that covers itself in a protective white sheath. Here is more information on that: