Our local Fairfax and Prince William Counties plan to spray for the fall cankerworm, Alsophila pometaria, or ‘inchworm’ this coming spring as they have done annually for many years. They will aerial spray Bacillus thuringiensis var. kurstaki (Btk) which will kill not only the cankerworm but also other native Lepidoptera (butterfly and moth) larvae. According to Cornell University, “More than 150 insects, mostly lepidopterous larvae, are known to be susceptible in some way to B.t.” That’s a huge amount of butterfly and moth larvae species affected, including innocuous species already in decline. It is also a lot of food loss for our feathery friends that are increasingly stressed by habitat degradation. Caterpillars are the main food source for migrating birds and also for breeding birds and their hatchlings. Did you know that it takes up to 9000 caterpillars to raise a single clutch of chickadees?
Fairfax County states on their website that 5000 acres of trees have been defoliated in the past. However, the North Carolina State University site referenced by Fairfax County indicates “cankerworms generally don’t kill trees”. It’s not clear how the County defines defoliation, as our native trees are hosts to many native insect species. Oaks, for example, support nearly 600 species of Lepidoptera.
This past spring The Connection ran a story on the debate over the spraying. Local entomologist Ashley Kennedy said that the spraying was not necessary and it costs Fairfax County about a half a million dollars annually. The County sprayed 2,200 acres of residential area in the spring of 2014. The primary reason, the County explained, was because the caterpillars were a nuisance to people.
Do we really need to be spraying? Could our tax dollars be better spent? I believe this is a woeful waste of our money as cankerworms are generally not killing trees and they are an important food source for native critters, particularly birds. Additionally, the spraying causes unintended consequences to many other caterpillar species as all pesticides kill indiscriminately.
The Audubon Society of Northern Virginia is petitioning Fairfax County and Prince William County to end the spraying of our native fall cankerworm. Please consider signing this petition to reduce County spending and to end this attack on our ecosystem: Audubon Community Petitions