Emerald Ash Borer
Infestations in Chapel Hill and Durham!
In 2019 we began finding emerald ash borer (EAB) infestations in Chapel Hill, Durham, and Chatham County. EAB will do here what it has done elsewhere since its discovery in Michigan in 2002. Whether the ash trees in your neighborhood are plentiful or few and far between, it doesn’t matter. EAB is projected to kill them all. An updated national map can be found here. The pins in the adjacent map shows where we have seen EAB exit holes in infested ash trees during the course of our local tree assessments since 2019.
While we often recommend letting the ash trees die if they are in wooded areas where tree decay and failure won't pose a hazard to persons or property, ash trees should otherwise be treated or removed before they show significant beetle damage or dieback. Beetle-damaged ash trees can otherwise become much more difficult, hazardous, and costly to remove.
Treatment options, considerations, and additional information found below.
map updated 10/24/2020
Trunk Injection: For the most reliable, fastest acting, and longest lasting protection, and for valued trees larger than 10-inches diameter (at breast height), The Treeist, as well as several other local tree care services, offers emamectin benzoate trunk injections. Until all untreated ash trees in our area die EAB populations will be high and we regard this as the only highly reliable method for saving ash trees during this time. The effects of injection treatments are longer lasting (studies show it to be effective for two to three years), and the small amounts of insecticide are more precisely delivered to the target tree. Costs for this treatment vary with the diameter of the tree. The next opportunity for treating ash trees is Spring 2021, when the trees begin to leaf out.
While we can guarantee that our treatments will follow best practices known to be effective against EAB (including the International Society of Arboriculture’s Best Management Practices, Tree Injection, 2015, and product labels), we cannot guarantee the survival of individual trees. Treatments are most effective when applied preventatively, before the beetles have extensively damaged your trees.
Soil Drench: Imidacloprid soil drench is a cost-effective do-it-yourself treatment that can be done on an annual basis with no special tools. An Ohio study has shown that imidacloprid applied at the highest allowed application rate was effective on trees up to 22” dbh (“diameter at breast height”). While not currently locally available under the most effective formulations/labelings, this insecticide is widely available online (currently as Quali-Pro Imidacloprid 2F, as Criterion 2F, and as Lada 2F). One gallon of any of these formulations is sufficient to treat three 15” dbh trees every year for seven years. Trees are ideally treated in the spring, but summer and fall applications can also be effective. Soil drench applications are slower-acting than the alternatives, and is not as reliable as the trunk injection treatments below. With current EAB pressure so high throughout Chapel Hill, Hillsborough, and Durham we are recommending trunk injections instead; after EAB kills nearly all of the untreated trees, beetle populations will crash and soil drench treatments promise to be an effective and lower-cost maintenance option. Product label instructions must be read, understood, and followed.
Trunk Spray: As a (faster acting but more costly) alternative to soil drench treatments, the root flare and lower trunks of trees can be sprayed yearly, in the tree’s growing season, with dinotefuran. Only requiring a simple pesticide sprayer, this treatment can also be performed by a homeowner. Dinotefuran can be purchased here or here as Safari 20SG, with the recommended bark-penetrating surfactant (Pentra-bark) purchased here. A 12-ounce jar of Safari 20SG is sufficient to provide one year of protection for three 13” dbh trees. Product label instructions must be read, understood, and followed.
Beyond the product label directions, this recent fact sheet is the best we've seen for further discussion and directions for the insecticide options. As a companion, this fact sheet gives information on potential side effects and hazards of the relevant EAB insecticides. We recommend treatments when the particular tree is highly valued, or when removal would otherwise be required at high costs.
For help identifying ash trees, go here.