I received an e-mail message over the weekend from a homeowner asking what kind of large beetles could be emerging from firewood stored in an unheated garage. I replied there were two possible candidates: painted hickory borers (Megacyllene caryae) and banded ash borers (Neoclytus caprea). In response, the homeowner sent some very clear pictures yesterday: they were painted hickory borers.
Although both borers are "longhorned beetles" (family Cerambycidae); so named because of unusually long antennae, only the painted hickory borers sport long antennae. Banded ash borers have relatively short antennae for a longhorned beetle.
Neither of these native beetles presents a risk to wood furniture, flooring, paneling, or other processed wood in homes, or wood used in home construction. They are just nuisance pests if they find their way into homes. However, their sudden appearance can be a surprise and cause concern; particularly inside log homes.
Painted hickory borers will only infest dead trees that died within one year or raw wood (e.g. firewood) that has been cut for less than one year. They target a wide range of hardwoods including their namesake host as well as ash, black locust, hackberry, honeylocust, oak, Osage orange, walnut, butternut, and occasionally maple.
Banded ash borers will only infest trees that are dying or recently dead and they have a much narrower host range. The borer will infest ash, as their common name implies, as well as hickory, elm, and occasionally white oak. Their narrow host range coupled with a strong dependency on ash could present a challenge for this borer given the loss of ash to emerald ash borer (Agrilus planipennis).
Both beetles are considered forest products pests because they may infest fresh-cut logs used for lumber or firewood. However, they also play an important role in forest ecosystems. Both serve in the "clean-up crew" by starting the biodegradation process to convert large wood fibers into smaller organic particles that ultimately support soil microorganisms important to soil health.
On a final note, this is also the time of year when we get incorrect reports that locust borers (M. robiniae) are emerging from firewood in and around homes. This is another longhorned beetle that is closely related to the painted hickory borer and both beetles share similar markings. It is common for homeowners who are relying on online identification resources to make an incorrect ID. However, painted hickory borers emerge in the spring and locust borers emerge in late summer to early fall at about the same time common goldenrod (Solidago canadensis) is in full bloom. In fact, locust borer adults are most easily spotted on goldenrod partaking of the pollen and nectar.