PEST ALERT - Emerald Ash Borer (EAB)

The emerald ash borer (EAB) has been found in St. Charles County, marking the destructive insect’s first known infestation in the St. Louis area.

EAB was first found in Missouri in the summer of 2008 south of Greenville at a campground on Lake Wappapello, says Hank Stelzer, University of Missouri Extension state forestry specialist. Since then, EAB has been found in 11 Missouri counties, most notably in the Kansas City area.

Left unchecked, EAB is fatal for all three of the state’s native ash trees—blue, green and white ash. Pumpkin ash, a popular ornamental tree, is also susceptible. While mountain ash and prickly ash have “ash” in their name, they are not true ash trees and are not at risk.

“Over the years, ash trees were a species of choice to replace the American elms that were lost to the Dutch elm disease,” says Stelzer. “Plus, they hold up well in urban environments.” Until now.

The infestation in St. Charles County was discovered by an employee at an industrial park on Highway N, a few miles south of Interstate 64. He noticed a declining ash tree in the parking lot. He looked closer and found the distinctive D-shaped exit holes. He then called the urban forester from the Missouri Department of Conservation. The forester, along with entomologists from the Missouri Department of Agriculture, collected a good adult specimen. USDA personnel in Brighton, Michigan, confirmed it was EAB.

The crown of a tree with EAB will be mostly dead within two years of showing symptoms. This could be a problem if the tree is providing summer shade for a home or playground.

What are homeowners and communities to do?

“The first thing a homeowner can do right now is take an inventory. Communities too,” says Stelzer. “Do they have ash trees? If so, how many? And what is their general condition?”

Stelzer says another important question to ask is, “Am I willing to invest the time and money to protect my ash tree?”

Available treatments only protect the tree from attack. Once you stop treating a tree, it will once again be vulnerable. “If that tree is providing shade to your home, then I think the cost of losing that shade in terms of an increased energy bill justifies the expense of protecting the tree,” says Stelzer.

For communities, weighing the costs versus the benefits might seem more abstract, he says. However, the USDA Forest Service has developed a software tool called i-Tree that helps communities of all sizes strengthen their urban forest management and advocacy by quantifying the environmental services that trees provide.

The Kansas City urban forester did just that and was able to get the city government to reallocate $1 million dollars to protect their ash trees,” Stelzer said.

Once you have determined you have an ash tree worth saving, the next thing to do is to take action if you are within 15 miles of a known infestation, he said. There are two options for protecting an ash tree with insecticides: “A homeowner can apply an over-the-counter product each spring, or a professional arborist can apply a registered insecticide providing protection for up to two years.”

If you have decided that a particular ash tree is not worth the long-term investment of protection, then consider replacement. Stelzer has two pieces of advice when it comes to replanting.

First, make sure it is the right tree for the right place. “The replacement tree should be a native species that is adapted to growing in the St. Louis area, and it should be planted in a place where, as it grows, it will not interfere with utility lines or building foundations.”

Second, if you are replacing more than one ash tree, vary your tree selections. “Just like diversifying your stock portfolio, planting a variety of species will help minimize future losses when the next invasive insect or disease shows up,” Stelzer said.

For more information about EAB, go to the University of Missouri Tree Pests website.  “This is an ever-changing situation,” Stelzer said. “The best way to stay informed is to check out our website on a regular basis.”