Emerald Ash Borer Beetle Confirmed in Baldwin City, Local Scientist Says

By Roger Boyd

The Emerald Ash Borer (~Agrilus planipennis~) is a small metallic green beetle native to China and first discovered in the US in 2002 in Michigan. It is often referred to as EAB and had probably been in the US for 20 years before discovered. The adult beetle is about 0.3” long and metallic green. It is elongate rather than short and wide like the larger Japanese Beetle. Due to its small size, the adults are not commonly seen but their damage is easily seen.

As the name implies, they feed on ash trees. The most common species in this area is Green Ash, but we also have native White Ash. Nurseries have also sold hybrid ash trees. All of them are susceptible to EAB. The beetles were first discovered in Douglas County in 2015, and since then there have been over a thousand trees infected and removed in the city of Lawrence.

In spring the adult beetles emerge, mate, and lay eggs on the bark. The eggs hatch and the larvae burrow under the bark. The larvae feed on the living part of the tree called the phloem which is between the bark and wood. Wood is actually largely dead tissue and not what the larvae feed on. As the larvae feed on the phloem they cut off the flow of nutrients from the tree leaves down to the roots. This process is called girdling. As the larvae do this, the tops of the tree die first. During the second year the tree will often sprout new growth on the lower to middle trunk of the tree.

In most cases, the tree will die, or at least the upper parts of the tree will die, within 2 years of infestation. Once these upper dead limbs are noticed it is too late to save the tree. If the tree is not removed fairly quickly it will simply be producing adults to infest other ash trees in the neighborhood. Healthy ash trees might be saved by treatment with several commercial chemicals, the main ingredient being Imidacloprid but it can be expensive and must be applied annually.

Scientists are predicting that 100% of the ash trees (native or introduced) will be infected and die. Ironically, the older larger trees will not die as quickly from EAB as they have larger trunks and it takes longer to kill enough phloem under the bark to kill the tree. The most susceptible trees are probably 20-30 years old (8-15” in diameter) as enough of the phloem can be destroyed in 1-2 years to destroy the tree.

If you have an ash tree in your yard, examine the upper limbs. If you see any dead limbs, then look at the trunk. Do you see new branches coming out of the trunk? Do you see cracks in the bark? Pull some of the bark off, and if EAB is present there will be conspicuous “S-shaped” tunnels eaten into the wood under the bark. As the adults exit, they leave a “D-shaped” exit hole. If you have dead limbs, new growth, S-shaped tunnels under the bark, then it is time to remove the tree. 

If you have an ash tree that does not show these symptoms then there are three possibilities:

1. It’s not an Ash tree;

2. You can try to save the tree using treatments that may or may not save the tree;

3. You could remove the tree as a pre-emptive strategy.

Unfortunately, now that the beetles are here in Baldwin City it is inevitable that the EAB will get to them. There are two potential impacts if the dead or dying trees are not removed: 1. The dead limbs may fall on your house, garage, vehicle, other structures, or people; 2. The infected trees will infest other trees in your yard or neighborhood. The EAB acts quickly, so you must act quickly as well.

Keep in mind that even if the tree is in the right-of-way in front of your house or alleyway, it is still the responsibility of the land owner to care for or remove those trees. Once the tree is removed you can consider replacing the tree with something else but make sure you do not plant another tree under an overhead power or cable line. Use Call Before You Dig (811) to check on utility placement as well. 

The Baldwin City Tree Board recommends not planting more maples in town as having too many of a single species is an invitation to disaster. All trees have potential pests, but native trees are probably the best replanting choices. Some of the trees the Tree Board recommends as sturdy, native trees are: Bur, Red, Black, or White Oak. Hackberry, Honey Locust, American Linden, Sweetgum, and Black Walnut also do well in this area and do not seem to be susceptible to major pests. 

Article written by Roger Boyd, President of the Baldwin City Tree Board. All photos by Roger Boyd as well, except the Adobe Stock image of the Emerald Ash Borer Beetle. Click or tap on the image of the beetle for more photos.