“Bt kills many other species of forest caterpillars which serve as an important food source for insectivorous migratory birds.”
— U.S. National Park Service
Despite concerns voiced by residents and the Audubon Society, Fairfax County conducted aerial and ground spraying on Monday, April 22, using the pesticide Bacillus thuringienisis (Bt) to kill the canker worm moth in six areas of the Mount Vernon Magisterial District, including the Hollin Hall and Paul Spring Parkway area in the Fort Hunt neighborhood.
Spraying was also conducted in other areas of southeastern Fairfax County. Some 1,965 acres were scheduled to be sprayed overall. Surveys conducted by the county last year indicated that the canker worm moth has dramatically grown in numbers and, if not controlled, will cause the defoliation and eventual death of many trees in the older sections of the county.
However, some Mount Vernon area residents and non-profit environmental advocates expressed concern about the potential impact on humans, pets, wild birds, and all insects and the timing and cost benefit of the program. Some raised the issue of the priority; should it have been approved by the Board of Supervisors (it was by unanimous vote) ahead of other programs suffering from budget cuts, and whether the county staff consulted sufficiently with locally affected residents.
County urban forest coordinator Troy Shaw, responding to questions about the adequacy of information outreach, said, “This past February and March we conducted Mount Vernon area informational hearings, including at Sherwood Hall library and in the Tauxemont neighborhood. We also sent out a letter to residents, and businesses in the affected area describing the program and asking whether or not they wanted to opt out of the program. We then followed up with a postcard to affected residents announcing the dates of the spray program.” Street signs posted in the Fort Hunt area also announced the program.
SCIENTIFIC RESEARCH on the Bt pesticide provides evidence that there are no significant adverse affects on humans or pets. Studies have illustrated that small numbers of humans and pets have been adversely affected, but not in sufficient numbers or circumstances to warrant preventing its EPA registration and use in the U.S. for agricultural or urban/suburban tree protection reasons. The urban forest Bt spray program is also being conducted in the Richmond area and in the Charlotte, N.C. area.
The U.S. EPA published an assessment in a Report issued on Sept. 28, 2011 (EPA-HQ-OPP-2011-0705, Case #0247): “The Agency believes that Bt … likely is a substance that would not produce any effect in humans similar to an effect produced by a naturally occurring estrogenic substance.” This assessment documented 40 cases of adverse effects on humans and pets; 11 were pets; 29 on humans. The circumstances on humans included accidental spraying of those doing the actual spraying, and minor allergic reactions on those in the direct line of the spray. A U.S. Department of Agriculture, Forest Service Report concluded as a result of its research on the human health effects of aerial and ground spraying of Btk (Kurstaki variety): “Btk are likely to cause irritation to the skin, eyes, and respiratory tract; however, serious adverse health effects are implausible.”
Not everyone agrees with the safety assurances , or the need for the program which has been in use in the county since 2003.
Liz Reiley, long time resident of the Paul Spring Parkway neighborhood, wrote to Shaw, enclosing excerpts from a Journal of Pesticide Reform report that raises questions about the health effects of the Bt spray program.
“Its alleged (the Bt spray program) not to be harmful to people and animals …. I am always skeptical of these claims — when there are harmful consequences of aerial spraying it is usually disclosed down the road. … Aerial spraying in our neighborhood has the potential to affect children and adults years from now and we wont know it; I just think that it is more prudent and safe for all concerned to conduct very focused ground spraying,” Reiley said.
Catherine Voorhees, Hollin Hall resident, said, “ We shorten the hours of access to our libraries and cut other county programs yet go ahead with an aerial and ground spray pesticide program of questionable priority.”
The Audubon Society sent a letter to the county objecting to the spraying program saying that the Bt pesticide will not only kill the canker worm moth but all insects including ones relied on as a source of food by wild birds, and all moth and butterfly caterpillars, including endangered ones.
The U.S. National Park Service does not allow Bt spraying for canker worm on its federal properties along the nearby Mount Vernon Parkway: “The NPS does sometimes use Bt spray to treat infestations of the non-native gypsy moth; it does not use the insecticide on native moth populations such as the fall canker worm or spring canker worm. Bt kills many other species of forest caterpillars which serve as an important food source for insectivorous migratory birds. The NPS has documented 480 species of macro-moths within the park, 11 of which are considered rare in Virginia. One moth, Abrostola Urentis, is known in Virginia only in the George Washington Memorial Parkway.”
Glenda Booth, president of the Dyke Marsh Wildlife Preserve, said, “Bt pesticide broadcast from helicopters will kill all moth and butterfly caterpillars, including species in decline. … Fall canker worms are native insects and their caterpillars appear when many songbirds migrate through northern Virginia, including the Dyke Marsh Wildlife Preserve. Birds are natural predators of these insects. The friends of Dyke Marsh hopes the county will adopt less harmful treatment, if one is really needed.”
COST OF THE OVERALL Bt spray program, according to the county, is $52,000 for aerial spraying, and $20,000 for ground spraying. The cost includes the use of helicopters and the cost of the Bt pesticide.
Jim McGlone, urban forester and member of the county’s Tree Commission, said, “Bt is a relatively benign bio-pesticide. ... Bt is a widely occurring soil bacterium that has been used since the 1920s as a pesticide … and approved for use in organic farming. … Fall canker worm emerges earlier than most other Lepidoptera, so effects to non-target species is minimized. … in the end I trust the EPA and the state agency regulating pesticides to make a reasonable , scientifically valid decision on the safety of applying Bt.”