Birches are some of the most beautiful landscape trees, but they have a serious enemy, the bronze birch borer.
These highly destructive pests wreak havoc on birches—gutting their inner bark and ultimately killing the trees. And they attack more than birches; oak, honeylocust, basswood, and maples are also susceptible to the damage caused by these flat-headed, bronze colored beetles.
So what’s the best way to protect your trees?
Early detection and action are essential—especially for landscape birches.
How Can I Identify Bronze Birch Borers and Their Damage?
Mature bronze birch borers are large, elongated, greenish bronze beetles between ¼ and ½ inches in length.
The invasive beetles are a problem throughout Connecticut, so all home owners with birch trees should keep a look out for the signs and symptoms of their damage.
Infestation first occurs in the upper limbs of trees before beetles begin to work their way down the trunks where they do their most deadly damage. Upper branch damage occurs in telltale spiral ridges that appear along the bark, and infected limbs show clear signs of leaf wilt and decline. However, since the initial damage occurs high in the tree, it can be hard to see from the ground. That’s why calling in a professional to inspect your birch trees can be helpful.
How and When Do Bronze Birch Borers Attack Trees?
Bronze birch borer beetles emerge in late spring from distinct “D”-shaped exit holes in the bark. Those exit holes are something to look for in spring – if you see anything suspicious, call in an expert.
Immediately, the beetles begin to feed on the leaves of the trees. They survive for two to five weeks, then they mate and the females lay small white eggs in crevices along the bark. Larvae hatch from the eggs in just a few days and immediately begin to chew through the outer bark until they reach the living layer of inner bark where they feed through summer and fall. As they feed, they create maze-like tunnels of damage that eventually strangle trees. Larvae overwinter under the bark and emerge as adults in spring.
What Can I Do to Protect My Birch Trees?
There are two methods of bronze birch borer protection for existing birches: good care and commercial chemical controls.
Good care is the first line of defense for your trees. The beetles are most attracted to stressed trees, and larvae do not feed as successfully on strong, healthy specimens. Keeping your birches properly (but not overly!) fertilized and watered will help them ward off these pests.
Trees with an early infestation can survive if treated with systemic pesticides. These chemicals must be administered by professionals, so it’s important to rely on a licensed arborist who is knowledgeable of bronze birch borer eradication.
Planting resistant birch trees is another solution. White birch varieties are most susceptible to bronze birch borers while river birches are more tolerant. Asian and European birch species are also resistant.
Keep an eye on your prized birch trees if you want them to remain free of bronze birch borers. Give them good care during stressful weather, and if you see the signs of damage, don’t hesitate to contact us. These pests are relatively slow to establish, so early detection and action can save your trees.