If you're the proud owner of a stand of ash trees, you may be dismayed at the sight of the telltale D-shaped holes and emerald beetles that unmistakably mark an infestation of the emerald ash borer. These highly destructive pests have already killed millions of ash trees throughout the U.S. and show no signs of slowing, with some estimating that these beetles will all but eliminate the domestic ash population within the next few decades.

While many advocate containment and quarantine as the best way to limit the spread of this scourge, you may be reluctant to cut down your beautiful, wide-canopied trees, especially if they still appear to be mostly healthy. Read on to learn more about these destructive insects and the factors you'll want to consider when deciding whether treating or felling your ash trees is the better option.

Why are emerald ash borers so harmful to ash trees?

As with many of the diseases, fungi, and insects that have decimated entire species of trees, the ash borer operates as a means of destruction by slowly damaging the tree over time and reproducing frantically. Two telltale signs of an ash borer infestation include D-shaped holes in your tree's bark and thin, squiggly lines between the bark and the wood of the tree. These holes are created by adult ash borers making their way into the tree, while the lines are often formed by larvae and young insects as they travel within the tree. 

A single ash borer or two is unable to cause significant damage to even a small tree, but these insects reproduce rapidly and can quickly eat away a tree's protective bark and disrupt the flow of water and nutrients from the roots to the leaves. As the tree loses leaves, it's less able to capture the sun's energy through photosynthesis. Ultimately, ash borers may eat away so much of a tree's vital structure that it dies, losing moisture until it is eventually felled in a storm or just begins to fall down piece by piece.

The wood or bark of a single infested ash borer tree, when transported as firewood or even just a few stray pieces of bark in the back of a pickup truck, can spread these ash borers much farther than they normally travel on their own. Many states have enacted restrictions on the use of "home-grown" firewood in campsites or parks to protect the ash stands within these parks.

How can you decide whether to treat an ash borer infestation or remove the affected trees? 

When caught relatively early, an infestation of ash borers can be treated by eradicating the insects with insecticides and then following up this treatment each year to prevent a recurrence. These insecticides are injected deep within the tree, where they can operate to kill ash borers in all stages of life. Treating your tree each year after the initial treatment will ensure it has the tools it needs to regenerate itself.

However, if this treatment isn't started until after much of the tree has already died, it may be too late. Even eliminating ash borers' ability to do further damage may not stop the death of your tree if these borers have been at it for years. Some signs your tree may need to be cut down include a major thinning of the crown (or the leafed area at the top of the tree), an excessive number of woodpecker holes that can indicate a major and long-term source of ash borer grubs, and woodpecker "flecking," or removal of strips of bark in an effort to get even closer to this food supply. 

Contact a tree service like R. L. Elliott Enterprises, Inc. if you're concerned about the health of trees on your property.