Alison Arnold: Invasive Pests in Urban Landscapes

Jul 20, 2017

This week, BPR gardening expert Alison Arnold tells us about an invasive pest, the emerald ash borer.

Q: I understand you attended a workshop by the NC Urban forest council last week on invasive pests in the urban landscape? What were some of the highlights?

A: They mainly talked about the Emerald Ash Borer and the Hemlock wooly adelgid but they also addressed beneficials insects and their important role in managing both common and invasive pests in the landscape. A lot of the participants were landscapers, nursery growers, land owners, property managers, arborists and other tree health care professionals.

Q: Emerald Ash Borer –can you describe it for us?

A: Will like the name says it’s a metallic emerald green colored beetle about 1/2” long by 1/8” wide and like a lot of invasive pests they are small but can cause a lot of damage. Emerald ash borer also known as EAB has been responsible for the death of 50 million ash trees in 24 states and 2 Canadian provinces since it was first detected in 2002.

Q: Wow! That's aggressive. So where did it come from and how does it kill the trees?

A: EAB is native to Asia and was first detected in 2002 in Michigan, confirmed in NC in 2013 and was thought to have come in on solid wood packing materials. The adult beetles emerge May – mid June, they mate and then female lays 65-90 eggs in the cracks of the trunk and major branches. Once the eggs hatch the new larvae tunnels through the bark into the cambium region (just under the bark) where they feed.  This feeding is where the damage occurs.

Q: What type of damage is it?

A: They create serpentine or S-shaped galleries under the bark which cuts off vital water and nutrient flow in the tree.

Q: What are the symptoms if you are looking for Emerald Ash borer in ash trees?

A: Typically the initial infestation takes place up in the live crown of the tree. The beetle makes a D shaped hole in the bark and while that’s a unique shape it’s only 3/16 of an inch in length and can be really hard to see, especially in tall trees – 60 feet up. Woodpecker activity, crown die back and the S shaped galleries under the bark are signs although by this time the tree is usually beyond help.

Q: What should people who own ash trees do if they suspect Emerald Ash Borer or have concern?

A: Consulting arborist or forester is a good first step .. you want to get confirmation. If you have specimen trees treating preventatively can be a good idea since treatment isn’t effective once the tree is infested and in decline.

Q: How does a pest like this get around?

A: Emerald Ash borer adults fly short distances but they also travel in or on vehicles and in firewood or untreated Ash lumber.  Unfortunately it wont be long, a couple of years maybe, before we really see the presence of EAB in some of our forests where Ash is prevalent. Both the federal and NC forest service with other cooperators have great online resources for more information.