picture taken by James Zablotny Ph.D. from USDA APHIS Plant Health website
Gallery and exit hole. Picture taken by Gerald Wheeler, found on USDA APHIS Plant Health website
picture of Agrilus planipennis larva taken by S. Ellis, found on USDA APHIS Plant Health website
Emerald Ash Borer: Agrilus planipennis
Emerald ash borer (EAB) which had first been discovered in the Midwest near Detroit in 2002 has spread to 22 states plus Ontario and Quebec. It has destroyed tens of millions of ash trees. As of 2014 EAB has been found as far south as Georgia and Arkansas stretching to Massachusetts, Wisconsin, Iowa and as far west as Colorado. In July, 2012, it was identified in Connecticut. Belonging to the buprestid beetles many adults in this family exhibit wings with a metallic glint as does EAB. The wings of Agrilus planiplennis are iridescent green. What is atypical is its adult size which trends smaller than its cousins attaining one-third inch though may potentially grow nearly one inch in length. EAB is from China, Japan, Korea and eastern Russia. It is thought, as with Asian Longhorn Beetle, to have arrived in wooden packing material and palettes but specifically in the case of EAB made of ash trees.
In the New World EAB lacks predators and quickly bred uncontrolled. EAB can fly up to one-half mile during its adult phase. Shortly discovered here after the melee of Hurricane Sandy it has been suggested that the huge storm with big winds may have transported this marauder from on strong easterlies. However, movement of wood, particularly firewood may have been or could have contributed to its untimely discovery in Connecticut.
EAB's host are specifically ash trees (Fraxinus). Your mountain ash (Sorbus) will not be bothered. Fraxinus species tolerant of seasonal extremes have been utilized as street trees more so in the Midwest. That is a loss to be sure. But even more devastating is the impact on eastern forests where a number of Fraxinus species are part of the mix. There are numerous ash species. Both white and black ash occurs all forests east and sometimes just across the Mississippi River. Both occur in Connecticut. North Carolina hosts four species of Fraxinus. Single-leaf ash is native to Colorado. Fraxinus provides not only cover and nesting opportunities for birds but the seed is an important food for numerous species.
A ripple effect affecting many aspects of forest life is created by the death of ash trees. EAB is yet another among the growing list of assaults on forests which are increasingly stressed. Woolly adelgid has destroyed much of the hemlock ecosystem in Connecticut. The fungal malady, Dutch elm disease, White pine blister rust, chestnut blight, dogwood anthracnose among others have desecrated local woodlands. Climate change, too, with warmer temperatures and a changing hydrology is very much impacting forests and the complex web of life of which trees are a fundamental element.
Adult EAB with a life span of 3 to 6 weeks can be founding feed on ash leaves between the months of May and August. After mating occurs EAB adult insects lay small reddish brown eggs between bark plates and in crevices just under the surface usually in early July. Eggs may be single or found in groups. The eggs hatch within 14 to 21 days. The damaging larvae bore into the phloem with heaviest feeding occurring in August, September and into October leaving circuitous, S-shaped and zigzag markings under cover of bark. These damaged areas are called galleries. This scoring of the xylem disrupts the flow of water and nutrients from the roots to the crown of the tree. Most larvae, or prepupae overwinter in sapwood or inside bark. Death comes in two to four years after infection. It is an added misfortune that EAB has recently also been found on Fringtree, Chionanthus virginicus.
Unfortunately, for those of us who prefer not using insecticides, chemical methods are the only recourse to protect trees presently. And these insecticides may negatively impact native insect populations who also depend partly or wholly upon ash trees for survival. Best results will be when appropriate chemicals as sprays or injected into the cambium layer will be employed prior to infection. Prophylactic application will prevent problems before infection may occur for once Emerald Ash Borer has infested demise ensues quickly. If the canopy of an infected tree has lost 50% of its foliage the tree will be not be salvageable.
Specifically in Connecticut, presently a quarantine of ash wood, especially raw firewood has been imposed on New Haven, Fairfield, Litchfield and Hartford counties. Undoubtedly all of Connecticut's eight counties will soon be part of the quarantine if they haven't already been designated by the time of this publication. It is this writer's recommendation that all those who use firewood know with as much certainty as possible where your wood has originated and that your supplying source has integrity and is local. It is hoped that wood cutters and homeowners alike will respect the quarantine to help slow the spread of this devastating insect. Please be not only vigilant but try to embrace this new affront to and all of the sweeping negative impacts of various threats upon our fundamentally important forests.
penned by Wayne Paquette, March 2015