What to Know: Signs of Emerald Ash Borer Infestation

Many US cities are preparing for an Emerald Ash Borer, Agrilus planipennis (EAB) invasion. The EAB is native to northern Asia, but was discovered in Michigan and Ontario in 2002. The adult EAB has a bright outer mantellic green color, with copper colored abdominal. It is roughly half an inch long, and only one eighth of inch wide. The
EAB larva is milky white with bell shaped segments. Since it is discovery it has spread to over 25 states and most of eastern Canada.

The invasion continues to move west. Already 70 million ash trees have been infected and there is a chance of losing a large percentage ash trees in North America. The Texas A&M Forest Service (TFS) confirmed in December 2018 that there are EAB infected trees in Tarrant County.

The first step is to identify your trees to see if you have an ash tree that may be at risk. The TFS website has a useful identification tool that identifies trees by the leaf.

The main characteristics of ash trees is a compound leaf with five to nine leaflets (always odd numbered) that are smooth on the edges. The leaves (not referring to the leaflets) are also located opposite one another on the twig.

EAB will only kill ash trees, so there is little need to worry if you are fortunate to not have an ash. Otherwise you can monitor your tree and identify if your tree has been infected or not. When an EAB larva bores in to an ash tree, they create a winding S-shape path, called galleries. These galleries become visible when the bark begins to split. If your tree is infected, callous tissue will start to form causing the bark to become weak. Another thing to look out for is D-shape holes. After becoming become an adult, the EAB exits the tree and create the hole. You can recognize if your tree has been infected by checking for the S-shaped galleries and D-shape holes.

Homeowners can also observe if the tree has been infected by watching for epicormic shoots. Epicormics branches are small shoots that grow from previously dormant branches. If you can identify these factors on your tree, it is likely it has been infected and needs to be treated.

The typical recommendation is to treat ash trees when EAB has been located within 15 miles. To prevent EAB infection, a chemical pesticide such as emamectin benzoate or imidacloprid is injected at the base every 2-3 years to prevent the tree from becoming a host for EAB larvae. The current EAB outbreak is not yet confirmed within 15 miles of Arlington, but for those considering treatment of their ash trees the most effective timing is in the spring months. Most times homeowners do not notice the problem until it is too late, unfortunately.

Once the tree becomes severely infected the chance of recovery even with treatment is low and it is likely the tree will die within 2-3 years. If a tree must be removed, Arlington Forestry and  beautification supplies free trees to residents through the L.E.A.F program. To reduce the spread of EAB larvae, do not bring any firewood or ash wood into the area. Even after a tree is cut down the EAB larva can survive and continue to infect other trees. When you do store firewood, be sure to always keep it away from trees in case of any pests that may harm living trees.

Arlington does not have a large population of ash trees, and that makes for a lower risk of invasion. However, that doesn’t mean that you shouldn’t prepare and take precautions. Being observant of signs and knowing the preventions can help our city stay protected from the emerald Ash Borer.