Update on Emerald Ash Borer

Healthy White Ash Trees at Mountain Top Arboretum

On June 14, 2016 our final group of white ash, Fraxinus americana, in the Woodland Walk was treated for emerald ash borer (EAB).

A team led by Cornell University Forest Entomologist Mark Whitmore, Vern Rist (Healthy Trees) and Phil Lewis (USDA, APHIS, Arborjet) injected fifty more ash trees with insecticide.  The insecticide travels through the phloem just beneath the outer layer of bark, killing EAB as it feeds. Ash is a wind pollinated tree and lacks nectaries so this injected treatment will not harm pollinators nor other insects besides EAB.

When you visit the Woodland Walk, you will be able to identify the ash trees in our study:  fifty trees were treated in 2014 and are taped with a blue ribbon, fifty trees were treated in 2015 and are green-ribboned, and fifty trees have now been treated for 2016 and have purple ribbons.  Outside the Woodland Walk throughout the Arboretum, you will notice other ash marked with blue ribbon.  These ash have not been treated and are control specimens for the project.  You can evaluate the effectiveness of the treatments by comparing the untreated to the treated trees.

Mark Whitmore studies each tree for canopy decline (the amount of defoliation in each tree) and signs of woodpecker holes.   Hairy and downy woodpeckers feed on the borer in ash trees so woodpeckers holes are a good sign of an infestation.  Mark gives each tree a grade of 1-5 based on the tree’s canopy decline.  Mark began taking data on all 150 trees in 2014, and he will use this data for studies of EAB in ash.

Many of our ashes seem to have responded well to the treatments are are looking healthy and beautiful.  Because the treatment’s effectiveness lasts two to three years, injections will begin again in 2017 for the blue-ribboned 2014 cohort.  Mark, Vern, and Phil will continue to work with us as we save these majestic and important trees.

With the decision to treat as many of our ash trees as is feasible in a forest setting, the Arboretum hopes to claim a future for ash on the mountain top and advance knowledge about the effectiveness of treatment regimens for both private and public landowners.  Live ash trees will be wonderful for visitors to see, and will produce a valuable genetic resource in new seed. We may be able to reestablish ash as a forest tree species in the future.

The Arboretum would like to thank members of its important volunteer corps: Master Naturalist volunteers Deb Allen and Laura Pierce assisted in planning and implementing the study. Work included counting, tagging, measuring, and data logging of large stands of old growth ash trees.