There Might Yet Be Hope for Our Ash Trees
By Chris Williams on June 16, 2016.
If you have an ash tree or two on your property, you’re justifiably worried about the emerald ash borer. This ½-inch long wood-boring beetle from Asia is decimating all types of ash trees across the Eastern and Midwestern U.S. It was first found in the Detroit area in 2002 and was later discovered in Massachusetts in August of 2012.
In 2014, Massachusetts instituted a state-wide quarantine in an attempt to stop the spread of this beetle (see MA and NH Counties are Quarantined Because of the Emerald Ash Borer). This quarantine on the distribution of ash trees, firewood, wood chips, mulch, and anything else ash remains in effect. The emerald ash borer has already killed hundreds of millions of ash trees in North America and the economic damage is staggering.
Emerald Ash Borer Beetles Are Active Now
The metallic green emerald ash borer beetle emerges from infested trees in late May or early June, leaving a D-shaped exit hole behind. The female lays eggs in the bark of the ash tree. Hatching larvae bore into the tree and tunnel into and feed on the cambium layer just under the bark. This beetle attacks stressed as well as healthy ash trees and its feeding can kill a tree in 1-5 years.
The main reason that the emerald ash borer has been able to cause such devastation in the U.S. is that it was accidentally introduced into this country from Asia without any of its natural enemies to keep the population in check. Researchers from USDA visited China early on, looking for predators and parasites of the emerald ash borer in its native range. They discovered 3 tiny parasitic wasps that attack the beetle’s eggs and larvae.
Newly Released Parasitic Wasps May Save the Day
USDA’s Agricultural Research Service, the U.S. Forest Service, and the University of Massachusetts reared one of the parasites and have since released the wasps into 22 U.S. states that have emerald ash borer. Over the course of the 7-year study, the researchers saw a 90% decline in the beetle larvae in infested trees attributed to the newly released parasites with help from native parasitoid wasps. The team believes that once the parasitic wasps are released in an area, that they will reduce the populations of emerald ash borer and perhaps prevent outbreaks in newly infested areas.
Source: TN Dept. of Agriculture | Forestry Images