Emerald Ash Borers (Agrilus planipennis), also referred to as EAB’s, are introduced invasive beetle that is a threat to our native ash trees. The beetles themselves are small and an attractive metallic green color. They are native to Russia, Northern China, Japan, and Korea, where the native ash trees they evolved with have ways of dealing with them so they are not killed which our native ash trees do not.
They were accidentally introduced into North American in 2002 near Detroit, Michigan as part of cargo shipments. Since then, they have spread into more than 20 states. They reached Fairfax, Virginia in 2003, and were believed to have been eradicated after the region was put into quarantine and all infected trees were destroyed. However, they reappeared back into Fairfax and then Arlington in 2008, having broken quarantine. Since then, they have started wiping out all our native adult ash trees, and some report have started to also infest fringetrees.
The spread has likely due to the adult beetles being good strong fliers and their propensity to be spread by transporting firewood. This has led to “Don’t Move Firewood” campaigns and using only local firewood in many localities.
They larva bore into ash trees just under the bark, feeding on the phloem and xylem tissues that feed the tree. They can thus starve the tree or even girdle them so they die off. About 2 years after infestation, the trees start to lose canopy and within 3-4 years the ash trees are dead.
|The D-shaped holes of emerging Emerald Ash Borers.
The adults complete their life cycle within a year, sometimes two, leaving telltale D-shaped openings as they emerge from the tree. Eventually after woodpeckers have searched for the larvae to feed on and as the bark falls off, you can start to see the damage that the borers due to the tree itself with tunnels all over just underneath the bark.
|The galleries and tunnels of Emerald Ash Borers just below the bark of an ash tree
Some jurisdictions such as Arlington are trying to protect the ash trees by treating the trees by injection to kill off the borers, but this can also affect other native tree feeders. Right now Arlington is treating 19 significant ash trees to protect them and so they can act as the seed source for new ash tree saplings, which until they get to certain diameter, will still provide wildlife value.
This May, parasitoid wasps which exclusively feed on emerald ash borers will be released as a biocontrol. These wasps are the size of a grain of rice and are completely harmless to humans. They have been tested and will only affect the invasive emerald ash borers and nothing else. These have been released and proving to be a great tool in the management of this invasive, including in Fairfax County last year.