Iowa Insect Information Notes

Wharf Borer

Wharf Borer

As the name implies, the wharf borer is common in the pilings and timbers of wharfs and docks and is most abundant along the coastal areas of the U.S. However, it is found in any wet, rotting lumber and is distributed throughout the country. The wharf borer is only an occasional pest of rotting timbers in Iowa.

An infestation of wharf borers is usually discovered when the adult beetles emerge from infested wood, often in large numbers. The beetles have a long, slender, parallel-sided shape and are slightly less than 1/2 inch long. Their color varies from dull yellow to reddish orange with the tips of the wing covers deep purple to black. Like many of the other wood boring beetles, the wharf borer has long antennae that are about half the length of the body.

The beetles can emerge from infested wood any time of the year but are most common in May through August. The females lay their eggs on the moist wood and the larvae tunnel into the wood. They feed and grow and produce long, winding tunnels inside the wood. Larvae grow till slightly more than 1 inch in length. The feeding action of the borers promotes the wood decay that also occurs in moist wood.

Any wet, rotting wood could be a source for wharf borers. Reported sources include timbers and posts in contact with moist soil, lumber or wooden items under leaking plumbing or other water problems and buried lumber. Wood wetted by dog urine is reported to be especially attractive to wharf borer beetles.

Control of a wharf borer problem requires correcting moisture problems and removing or replacing rotted wood such as decayed structural lumber or wood laying on or buried in the soil. Insecticide sprays are not effective for the control of this pest and their application would be a waste of time. Emerged beetles need only be vacuumed or picked up and discarded.

Updated 07/14/2005 - 2:53pm