Moth Caterpillars Overrun Island On Mississippi River

A highly-visible Mississippi River island just north of La Crosse has been overrun by a native pest that makes it appear as though all the trees on the island are dead.

The outbreak of fall webworms on Red Oak Island — just north of lock and dam 7 across from Dresbach, Minn. — can be seen by travelers on Interstate 90. The webworms have eaten the foliage on 90 percent of the walnut, elm and hickory trees on the island.

While the trees appear dead, Bobby Jackson, a forester with the U.S. Army Corps of Engineers, said that the trees should be back to normal in two to three years. He said birds and wasps should eventually eat all of the fall webworms.

“We’ve actually never tried to implement any chemicals to that area because it is a native pest versus an invasive pest,” said Jackson.

Fall webworms were first discovered on the island in 2003, and while they do spread, Jackson said he doesn’t expect a problem for other trees in the area since the island is so isolated.