Watching beloved trees wither and die

My grandfather’s generation lost the American chestnut to an exotic fungus that reduced this once mighty forest giant to old roots and hopeful shoots. 

My parents saw the American elms that used to shade our streets in broad allées felled by the one-two punch of Dutch elm disease and the elm bark beetles that helped to spread it. I am watching the next great killer of trees advancing through the woodlands today, and now that I know what I am seeing, I find it everywhere I go.

As its common name suggests, the emerald ash borer specializes in ash trees. The beetle prefers the foliage, but its larvae do the real damage beneath the bark where they savage the vascular network of the tree. 

Woodpeckers are fond of the beetle larvae, so much so that they expose the pale inner bark, a condition known as blonding. It is the work of these woodpeckers, rather than the fingernail shaped exit holes of the emerging adult beetles, that catches the eye. At this point, the beetle has done its work, and the tree is doomed. As there are more larvae than the woodpeckers can handle, the infestation spreads.

Since this exotic insect arrived from Asia in contaminated packing material in 2002, it has spread from southern Michigan to Colorado and the Canadian Maritimes. 

It was discovered in Connecticut in 2012 and is now in every county and nearly every town. It is too late to contain it, despite rigorous quarantine efforts and early detection efforts. 

It has killed more than 50 million ash trees in less than two decades since it arrived in North America. It will kill many millions more and threatens the entire native ash genus. The International Union for Conservation of Nature (IUCN) now lists the American white, green and black ash on its “Red List” of critically endangered species at high risk of extinction.

The white ash (Fraxinus Americana) is an important food source for many tadpole species because its leaves are low in tannins, but this is also what makes the tree susceptible to the emerald ash borer. 

The green ash (Fraxinus Pennsylvanica) was prized as an urban street tree to replace the American elm and is likewise low in tannins. It was this species, heavily planted around housing developments in the Detroit area, that allowed the emerald ash borer to increase and multiply once it became established. 

The black ash (Fraxinus Nigra) favors swamps and wetlands, and is culturally significant as the source of the ash splits for traditional native American and Shaker basket weaving. This species, too, is expected to be all but extirpated by the beetle, which kills quickly and prevents young trees from reaching maturity and reproducing.

It is hard to be hopeful when facing such odds. It is hard to watch the things we love wither and die and be powerless to stop it. It is important to witness their fates and to tell their stories, just as generations before mine remembered a time when chestnut blossoms fell like snow and elm trees spread their vaulting branches above city streets and country roadways.

Tim Abbott is program director of Housatonic Valley Association’s Litchfield Hills Greenprint. His blog is at www.greensleeves.typepad.com.