Fairfax County Aerial Spraying Jeopardizes Bird Populations

On behalf of the more than 4,000 members of the Audubon Society of Northern Virginia, we are writing to express our concerns about Fairfax County plans to spray for fall cankerworms in the Mount Vernon and Lee districts of the county. 

The mission of the National Audubon Society is to conserve and restore natural ecosystems, focusing on birds, other wildlife and their habitats for the benefit of humanity and the earth's biological diversity.

According to staffers in the county’s Urban Forestry Division, the Bacillus thuriengiensis (Bt) pesticide that the county will apparently spray from helicopters, will kill all moth and butterfly caterpillars, not just the caterpillars of the fall cankerworm.  This is disturbing because caterpillars are a major food source for many birds and have an important role in our ecosystems.

Cankerworms are native insects.  They hatch just at the time many species of songbirds are migrating through Northern Virginia, an excellent example of nature’s synchronicity.  These birds are traveling from their wintering grounds in South and Central America to their breeding grounds in the northern United States and Canada.  They cannot make the journey successfully without stopping to refuel.  Each individual bird can consume hundreds of caterpillars as it replenishes its body fat, which will provide the energy for the next stage of the journey.  Therefore, this spraying will kill off a major food source for thousands of migrating songbirds that will be arriving in the area at exactly the same time as the county plans to spray.  Birds are natural predators of these insects.  It is their “job” to keep the caterpillars at sustainable levels. 

It is our understanding that one of the county’s justifications for spraying for fall cankerworms is that these caterpillars can defoliate trees.  Tree experts tell us
that healthy trees are capable of re-leafing after defoliation, especially when
it happens in the spring.  Native trees have evolved with these insects and they would have died out if they could not withstand an abundance of caterpillars every now and then.

We also understand that the U.S. National Park Service will not allow the county to spray on its properties, in areas like the Dyke Marsh Wildlife Preserve, because of similar concerns.

As an organization whose mission is to preserve and protect birds, other wildlife, biodiversity and the natural environment, we urge Fairfax authorities to abandon the plan to spray for cankerworms and give the birds the chance to do the job for you, as nature intended. 

Should the county proceed with the spraying, we would ask concerned citizens in the affected areas to exercise their right to opt out of having your property sprayed with Bt.  Contact the Fairfax County Department. of Public Works & Environmental Services to ask that your property not be sprayed.

John L. Lovaas

Board of Directors,

Audubon Society of Northern Virginia