© 2023 St. Louis Public Radio
Play Live Radio
Next Up:
0:00 0:00
Available On Air Stations

St. Louis foresters take on invasive emerald ash borer

Forestry Commissioner Skip Kincaid points out the insecticide injections given to a tree in north St. Louis.
Eli Chen | St. Louis Public Radio
St. Louis city's forestry commissioner Skip Kincaid points out how the insecticide, intended to weaken emerald ash borer larvae, are injected into ash trees.

Residents of St. Louis may have come across an odd sight in their front yards this summer: workers drilling holes into trees and plugging up the holes with mysterious white tubes. 

The white, caterpillar-like larva of the emerald ash borer digs a D-shaped hole into an ash tree's trunk, later emerging as the bright green adult beetle.
Credit Missouri Department of Conservation

The workers are urban foresters from the city of St. Louis' forestry division. While the activity might seem suspicious, they're trying to help ash trees that are vulnerable to the invasive emerald ash borer. 

The green beetle from eastern Asia has invaded half of the United States and 25 counties in Missouri. Last year, it was found in both St. Louis and St. Louis County, and now officials are taking steps to eradicate the pest on city-owned property.  

After the emerald ash borer larvae begins to feed on an ash tree, the tree quickly "begins to dry up and die, and they become very brittle and dangerous," said Skip Kincaid, the city's forestry commissioner. Death will take place two to three years after infestation. 

Ash trees make up 17 percent of the city's street tree population, or more than 14,000 trees. The city plans to inject about a thousand trees with an organic insecticide, based on the extent of damage. The remaining will be removed over the course of five years, starting in July. 

One way to evaluate damage from a pest is to look for dieback, meaning brown leaves and dead branches. Forestry commissioner Skip Kincaid estimates this ash tree has suffered a "10 percent dieback," which is low enough to receive chemical treatment.

The city plans to spend $530,000 annually over the next five years to tackle the pest. Kincaid also urges homeowners with ash trees on their property to take action and help prevent the spread of the invasive beetle. 

"We want people to learn about the insect, to learn what it means for ash trees in their yard," Kincaid said, "and take proper steps to make a reasonable decision about whether it should be treated or cut it down and start over."

Eli is the science and environment reporter at St. Louis Public Radio.