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Only 2 Iowa counties remain without ash borer detections


Only 2 Iowa counties remain without ash borer detections

Jun 08, 2023 | 4:17 pm ET
By Jared Strong
Only 2 Iowa counties remain without ash borer detections
The emerald ash borer has been discovered in 97 of Iowa's 99 counties. (Photo by Dr. James E. Zablotny/USDA)

The emerald ash borer was recently discovered in Plymouth County in northwest Iowa — the 97th county to have a detection since the beetle was first confirmed in Iowa more than a decade ago, according to state officials.

The insect is native to Asia and was likely transported to the United States in wooden packing materials, the U.S. Department of Agriculture has said. It was found in Michigan in 2002 and in eastern Iowa in 2010.

The beetle’s larvae eat ash tree inner bark — the living tissue that transports nutrients and water. That damage can kill trees within two years.

Many of Iowa’s larger cities have implemented programs to fell thousands of ash trees on city property and in rights of way in anticipation of their deaths.

Two years ago, West Des Moines additionally began requiring the removal of ash trees on private property if they were likely to die after a beetle infestation, according to its website. The city offered new trees at a discount to residents to replace the ash trees, which were estimated to account for about 20% of the city’s tree canopy.

Only 2 Iowa counties remain without ash borer detections
This map shows what year the emerald ash borer was discovered in each county. (Courtesy of Iowa Department of Agriculture and Land Stewardship)

The discovery of emerald ash borer in Plymouth County was the fourth confirmation in a new county this year, according to the Iowa Department of Agriculture and Land Stewardship. The others were Monona, Osceola and Woodbury.

Northwest Iowa had been the remaining area of the state without widespread detections until about two years ago. The only counties without confirmations are Emmet and Palo Alto, near the Minnesota border.

The adult beetles are a distinctive metallic green color and about a half inch long. Ash trees that are infested often have fewer leaves, sprouts with leaves coming from lower parts of the trunk or main branches, and holes where the beetles emerge that are shaped like the letter ‘D’ and are about one-eighth of an inch wide.

Those who see evidence of the emerald ash borer in Emmet and Palo Alto counties can call the state entomologist’s office at (515) 725-1470.