Wetwood disease can be commmon of shade trees

An area on the outside of a tree trunk that appears to be stained white or looks wet during summer is likely bacterial wetwood. It is also known as slime flux.

Wetwood is a common disease affecting the central core or bark of shade trees, such as elm. The stain is caused by slime generated from fermentation pressure in wetwood infected areas. The slime oozes out through bark cracks, then dries leaving the white stain.

The wet appearing bark and ooze often create concern there is decay in the tree. While decay could be present somewhere within the tree, wetwood-infected areas actually inhibit wood rotting fungi due to lower oxygen content. And wetwood-infected tissue only slightly alters the strength properties of wood.