Emerald ash borer, or EAB, was first found in Minnesota in St. Paul in 2009. Since then it has spread across the Twin Cities, and it kills nearly every ash tree it infests if nothing is done.
If you have an ash in your yard, here is how to check it, what the warning signs look like, and why it pays to act before the tree dies.
First, is it an ash tree?
Ash trees have branches and buds that grow directly across from each other, in pairs. Their leaves are made up of several smaller leaflets, usually 5 to 11, along a single stem. On older trees, the bark has tight ridges that form a diamond pattern.
If your tree matches all three, there is a good chance it is an ash. Maples also have paired branches, but their leaves are single and shaped like a hand, so the leaf is the easiest way to tell them apart.
Signs of emerald ash borer
Thinning from the top down. The upper canopy loses leaves first, and you start to see more sky through the top of the tree each year.
Woodpecker damage. Woodpeckers feed on EAB larvae under the bark. They flake off the outer bark and leave light-colored patches on the trunk and branches. In the Twin Cities, this is often the first sign people notice, especially in winter.
Small D-shaped holes. Adult beetles leave through exit holes about 1/8 inch wide with one flat side, like a capital D.
Bark splits and S-shaped tunnels. Vertical cracks in the bark can show winding, S-shaped tunnels underneath where the larvae fed.
New sprouts low on the trunk. A stressed ash often pushes out clumps of new shoots near the base.
Why waiting makes removal harder
Once an ash dies, the wood dries out and becomes brittle quickly. Dead ash trees drop large limbs without warning, and they can snap in a storm that a healthy tree would handle.
Brittle wood also changes how a tree has to come down. Crews cannot safely climb a dead ash, so the job often needs a bucket truck or a crane instead. That can make the removal take longer and cost more than it would have a year or two earlier.
A good rule of thumb: if a large share of the canopy is already gone, removal is usually the safe choice. If your ash still looks healthy and is important to your yard, have an arborist look at it now and talk through your options.
Fall and winter are a good time for ash removal
Late fall and winter are a smart time to take down a declining ash. The ground is firm or frozen, so heavy equipment is easier on your lawn and landscaping, and it is easier to see the tree's structure with the leaves off.
A Tree Service has its own tree crane and bucket trucks, so we can take down dead or brittle ash safely, even when it sits close to a house, garage, or power line.
Keep ash wood local
Moving firewood is one of the main ways EAB reaches new areas. Do not haul ash firewood to your cabin or campsite. Burn it close to where it was cut, or have it chipped or hauled away with the tree.
What to plant next
When an ash comes down, it is a chance to plant something that will last. Choose a species that fits your space and soil, and avoid planting the same kind of tree your neighbors already have a lot of. A mix of species means one pest cannot wipe out a whole street again.
If you are not sure whether your ash is infested, or whether it is an ash at all, the ISA Certified Arborists at A Tree Service can take a look during a free estimate and give you a straight answer.