This letter is in response to The Gazette’s Jan. 4-10, 2018 article titled “Trees in County Continue To Be Targets of Insects.” This article is missing key information that Fairfax County residents need to understand.
As an ecologist, I believe that public policies such as pest management should be based on sound science. In the case of the Fall Cankerworm program, the scientific evidence to justify this insecticide spraying program is lacking. The program’s stated purpose is “to minimize tree mortality”. Yet the county only monitors Fall Cankerworm populations, and sprays where the populations are considered to be high. Where is the evidence that periodically high Fall Cankerworm populations are killing trees, or harming the health of Fairfax County’s forests?
Defoliation is not the same as tree mortality; the trees may lose some leaves in spring due to inchworms, but these leaves generally grow back within a matter of weeks.
The native Fall Cankerworm has evolved with our ecosystem, including our trees, wildlife, and other natural controls, for many millennia. The article’s parallel to the non-native Emerald Ash Borer is highly misleading, since that species was introduced from Asia and lacks natural predators here in the U.S.
We know well many of the things that are killing trees in Fairfax County, including land clearing and new roads, non-native forest pests, invasive plant species, and unnaturally high deer populations. But I have seen no evidence that Fall Cankerworms are actually killing our local trees. Fairfax County staff have not shown that Fall Cankerworm defoliation leads to tree mortality in the county; they do not even monitor tree mortality. Nor have they shown that the spraying program is improving forest health, or that it is a smart use of county taxpayer funds. With no scientific evidence and no measure of effectiveness based on the stated purpose of the program, the county has not met its burden of proof to justify continuing this costly program.
It is time for Fairfax County to cease its misguided monitoring and insecticide spraying program directed against the native Fall Cankerworm. Staff should focus their work on actions that would actually improve the health of our forests and woodlands, rather than target this native insect that helps to sustain many of our birds and other wildlife.
George C. Ledec, Ph.D.
Ecologist