The condition of trees and the tree canopy are important indications of the health of the local environment, whether urban or rural. One of the responsibilities of the Fairfax County Board of Supervisors is approval of the annual Forest Pest Management Program. Funding for the program is provided by a tiny portion ($0.0010 per $100 assessed value) of the real estate tax. That’s about $6 a year for the average homeowner, a miniscule amount to combat a potentially huge problem county-wide. 

Eleven forest pests or diseases are identified in the Calendar Year 2021 program, affecting trees from A (ash) to W (walnut); some of the pests have definitive, and creepy, names. The Asian Longhorn Beetle (ALB) is an invasive insect that infests many hardwood species and may threaten more than four million trees in Fairfax County. ALB larvae bore into the heartwood of a tree, and already may have caused non-recoverable damage before being discovered. Outreach to the public and updating the long-term ALB management plan are crucial to the battle against this invasive pest.

The Emerald Ash Borer (EAB) has distinctive and vivid green iridescent wings.  It has killed thousands of ash trees in the county, including in the Bailey’s Crossroads area of Mason District. EAB was first documented at a school site in the Wolftrap area in 2003, and both the Commonwealth and the federal government ordered removal of all ash trees within a half-mile radius of that site. Although tree injections with an insecticide can be effective against EAB, dead or dying trees still must be removed. For many years, transport of firewood was not allowed in Northern Virginia because of the possibility of moving EAB throughout the region. On Jan. 14, that quarantine was removed by the Trump Administration, but county and state experts still discourage transport of firewood, to prevent potential infestations.  

Fall cankerworm levels have fallen dramatically, so no areas will require treatment, but staff has been monitoring parasites and conducting defoliation surveys to combat the possibility of rising populations in the future.  Gypsy moth populations also have remained low, with no areas requiring treatment.  Two other pests — Hemlock Wooly Adelgid (HWA) and Spotted Lanternfly (SLF) — are newer to the management program. Native eastern hemlock is relatively rare in the county, but native stands in Dranesville and Springfield districts are being monitored closely. SLF is the newest, and very identifiable, pest, with white or light-colored wings, highlighted by bright red spots. SLF has not been identified in Fairfax County, but has been found in nearby Warren and Clarke Counties, and can be devastating to many crops and other flora. SLF has a preference for the Tree of Heaven, an extremely invasive and fairly common species here. Program funding will target removal and remediation of Tree of Heaven in 2021. 

According to county staff, most infestations found in the United States have been detected by tree care professionals or informed homeowners. With Spring approaching and yard work resuming, now is a good time to check your property for such pests, and report findings to the county’s Urban Forest Management Division.