Emerald Ash Borer: What are all those purple boxes?

By Naturalist Beth Moore

You may have noticed those purple boxes hanging from certain trees along certain roads. In order to appreciate what these boxes are for, we must first take a close look at an insect called the Emerald Ash Borer. In the past few years, there has been a lot of hype about the Emerald Ash Borer and the amount of the damage they can potentially cause. The Emerald Ash Borer (Agrilus planipennis) is a beetle native to Asia (specifically eastern Russia, northern China, Japan, and Korea). It was first identified in North America in 2002 in Michigan. Although the exact source of transit has not yet been confirmed, it is likely that it made its way to North America in the ash wood used to stabilize cargo on ships. Since 2002, infestations have been discovered in Illinois, Indiana, Iowa, Kentucky, Maryland, Minnesota, Missouri, New York, Ohio, Pennsylvania, Tennessee, Virginia, West Virginia, and Wisconsin. These infestations are responsible for the loss of over 50 million ash trees in the United States. It has also been found in two Canadian Provinces. These are likely not new infestations, but rather had just previously gone undetected and spread through our lack of knowledge of the insect’s existence in these areas.

Any introduced species (one that is not native to a given area) has the potential to become invasive (meaning it becomes successfully established in an area and its presence has an impact on native species). In the case of the Emerald Ash Borer, the beetle larvae bore into the trunk and major branches of native ash trees and destroy the water and nutrient transporting layers and eventually kill the tree. Initial symptoms are often difficult to observe as they occur at the canopy level. Infested trees do not immediately present obvious symptoms. Observation of the leaves as well as the trunk (where D shaped exit holes are present) are key in diagnosing an infested tree. Although research indicates the adults can fly at least a half a mile from the tree that they emerge from, transporting ash wood for use as firewood is also a major way infestations spread.

The more we increase our awareness of Emerald Ash Borer, the more we can do to try to slow down or prevent their spread. States that have confirmed the presence of the Emerald Ash Borer are under strict quarantine in which no ash wood may be transported. Additionally, states that have not yet confirmed the presence of Emerald Ash Borer, but could potentially become infested due to the presence of ash trees, are encouraged to continuously monitor for signs and symptoms of infestations. New Hampshire has not yet confirmed the presence of Emerald Ash Borer (the closest known infestation is in Kingston, New York), but ash trees make up about 15% of New Hampshire’s forests. Due to the current concerns with Emerald Ash Borer, as well as other insects such as the Asian Long Horned Beetle, New Hampshire has established a firewood quarantine to prevent the importation of non-treated wood.

So what does this have to do with the purple boxes that you see hung from trees? These boxes are hung in live ash trees to lure adult Emerald Ash Borers in close proximity. Although there has yet to be a confirmed sighting in New Hampshire, these traps help biologists to monitor ash trees for infestations. Since the adult Emerald Ash Borers take flight only during the warmer months, these traps are removed in the fall. How can you help? Don’t transport firewood and learn to identify signs of infestation. Together, we can hopefully prevent this insect from entering New Hampshire and killing our ash trees.