On Jan. 24, Fairfax and Prince William County spokesmen urged a Virginia House of Delegates subcommittee to allow localities to continue to kill caterpillars with broadcast spraying. At issue is Alsophila pometaria, the inchworm or fall cankerworm, a native insect that in its larval stage is a caterpillar, a major food source for spring breeding and migrating birds. Some view this caterpillar as a "nuisance" when it spins down from trees on a silken thread.
A coalition is trying to stop this spraying, which kills not just the target species but all butterfly and moth caterpillars exposed to the spray, Bacillus thuringiensis var. kurstaki (Btk). "This collateral damage is much too high a price to pay, when the focal animal is a natural element of Virginia's forest ecology," wrote the University of Connecticut's Dr. David Wagner, a world caterpillar expert.
Some spraying advocates contend that inchworms defoliate and kill trees. Opponents argue that it takes several years of severe defoliation to kill a tree, which is rare; that most trees releaf in one season; and that tree mortality has many, often undetermined causes.
Del. Kathy Tran (D-Fairfax) offered a compromise to her original bill to require residents to opt into the spray program, a reversal of these counties' current opt-out programs. The subcommittee rejected the bill on a party-line five to four vote.
The inchworm is a native insect, part of the natural ecosystem, not a destructive invasive like the gypsy moth. Government officials at all levels should understand the value of native insects and their role, critters that noted biologist E.O. Wilson said are "the little things that run the world." Killing caterpillars without documentation of real harm or without understanding their importance is inexcusable.
Ashley C. Kennedy, MS
PhD Candidate, Tallamy Lab
Dept. of Entomology and Wildlife Ecology
University of Delaware