There seems to be an increase in citizen concern about emeraldash borer (EAB) based on the number of calls and e-mails I have been getting this summer from people wanting simple answers to difficult questions. The difficult part is the nature of the eemerald ash borer itself and its direct impact on ash trees. We’re dealing with a beetle that is only a – to- inch in length and bullet-shaped, making detection difficult. Additionally, the state invasives maps show much of Vermont having an EAB presence but the actual number of visibly infested ash trees is still quite rare. Despite this it is still time to be concerned.
We are surrounded by a tree enemy whose early presence is hardly detectable but whose ultimate presence will kill most ash trees in Vermont. So it is worthwhile when driving around enjoying our beautiful trees to look for ash that show the first visible EAB signs —crown dieback. June through September is the “flight season,” when the beetles are dispersing looking for new ash to invade or to find mates. When an ash tree is attacked, the first sign is loss of upper crown leaves in the infected area. The power of this insect is in beetle numbers and as the tree continues to be invaded by EAB more and more damage occurs leading eventually (3-5 years) to death. Vigilance also needs to increase because moving firewood during this time can also spread EAB. Infested ash wood will have furrowed bark which may split and fall off showing the distinctive “S” shaped galleries. Bark may even have blonding (lighter colored with flat ridges) and the distinctive “D” shaped exit holes from beetle emergence. Wood in this condition should probably be left until fall before being moved and used.
So while the town must be concerned about infested hazardous ash along its beautiful town roads it is the tree in your yard that has prompted many emails this summer. Yes, you can inoculate ash trees to prevent invasion from EAB and several landowners have done that. But before you spend the money examine your ash tree for overall health, shape, and location. A healthy ash will have a full green crown, tight bark, and branches elongating as the tree grows this summer. Its shape should not include dead sections within the crown, any sort of major lean, the presence of other insects and/or diseases, or growth habits like “V” shaped branch crotches which can easily separate in high winds or heavy snow loads. Finally is your ash tree in a location that makes a significant contribution to your local landscape? All of these factors should be considered before treatment. Trees can be treated only by someone with a certified pesticide applicator’s license and there are five of them in the area between Rutland and White River Junction. Stay vigilant this summer. You probably will not find heavily infested ash trees but you just might notice ash with thinning crowns that were healthy last year.