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Washington State University
WSU Puyallup Symptom Identification Guides

Bacterial wetwood

A bacterial infection known as wetwood causes bleeding on trunks and large branches of oak trees and can resemble the bleeding associated with Sudden Oak Death. There are usually no other symptoms except in severe cases the foliage in the upper crown wilts and branches may die back. Most large elms and poplars have wetwood, and it is associated with branch death in large cottonwoods and with dieback and premature death of Lombardy poplars. Elms and poplars are not considered to be stem canker hosts for P. ramorum. Bleeding from wetwood is often associated with a crack, is black and watery, and has a foul odor. This is in contrast to bleeding caused by Sudden Oak Death, which tends to be reddish, more beady, and sticky. Wetwood is usually a secondary condition following a wound and occurs in the following tree species:

Conifers Hardwoods
True firs (Abies spp.) Maples (Acer spp.)
Pines (Pinus spp.) Oaks (Quercus spp.)
Poplars (Populus spp.)
Elms (Ulmus spp.)


Wetwood on white oak
Bacterial wetwood on white oak (Quercus alba). Randy Cyr, GREENTREE Technologies,
Wetwood on American elm
Wetwood with slime flux on American elm

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