Forest Pests: Insects, Diseases & Other Damage Agents

Wetwood (Corynebacterium)

From: Ostry, Michael E.; Wilson, Louis F.; McNabb, Harold S., Jr.; Moore, Lincoln M. 1988. A guide to insect, disease, and animal pests of poplars. Agric. Handb. 677. Washington, DC: U.S. Department of Agriculture. 118 p.

Importance- Poplars commonly develop wetwood, a water-soaked condition accompanied by a darkening of the wood. Premature death of poplars, especially of Lombardy poplar, has been associated with wetwood. Lumber made from wetwood is weaker than sound wood and is subject to checking and collapse during drying.

Look For: Water-soaked appearance of trunk. Slime flux at a wound or branch stub. Reddish darkening and water-soaked condition of wood when tree is cut. Branch dieback, tree decline.

Slime flux on affected tree.

Biology- Bacteria are implicated by many investigators as causing wetwood. Corynebacterium humiferum has been associated with wetwood of Lombardy poplar. However, we don't know the exact role of the many other microorganisms present in trees affected by wetwood. Furthermore, other investigators believe wetwood is formed by nonmicrobial process and supports a succession of bacteria after it develops.

Control:

• No control is known.
• Wetwood is not a problem if trees are grown on short rotations or if wood quality is not critically important.