What to Know: Protecting Your Ash Trees from the Emerald Ash Borer
By Arlington Parks & Recreation
Posted on October 25, 2019, October 25, 2019

 Emerald Ash Borer

North Texas cities have begun to prepare for Emerald Ash Borer, Agrilus planipennis (EAB), an invasive pest that was discovered in Tarrant County in 2018. 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 an 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 Texas A&M Forest Service (TFS) confirmed in December 2018 that there are EAB infected trees in Tarrant County. Arlington is currently outside of the 15 mile radius for the pest, meaning treating ash trees to prevent EAB is not yet vital, but homeowners should be aware of the issue and prepare for the eventual impact from the pest. Due to the presence of EAB, Tarrant County has been placed under quarantine that restricts the movement of hardwood out of Tarrant County. For more information on the quarantine, please visit https://www.texasagriculture.gov/RegulatoryPrograms/PlantQuality/PestandDiseaseAlerts/EmeraldAshBorer.aspx.

The first step for protecting your property 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 is injected at the base every 2-3 years to prevent the tree from becoming a host for EAB larvae. Emamectin benzoate is the recommended treatment as it does not contain potentially harmful neonicotinoids. Other common EAB treatments, such as imidacloprid, often contain neonicotinoids and are not recommended. Chemicals that may be applied as a soil drench are also not recommended due to the potential for runoff. For those considering treatment of their ash trees, the effective time to apply chemicals is in the spring. For this reason, homeowners should carefully monitor trees for signs of EAB or preemptively apply chemicals once EAB is detected within 15 miles of their location. Homeowners often do not notice the problem until the infestation is severe, and since treatment must wait until spring there may be no way to save the tree once it has begun to decline.

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 (estimated at less than 2 percent of the urban forest), 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.

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