The state will start spraying pesticides on more than 3,800 acres in Anne Arundel County to prevent an expected resurgence of gypsy moths.
The Maryland Department of Agriculture announced the plan after entomologists tracking the unwelcome insect's egg population noted a potential boom in the number of caterpillars concentrated in 15 areas, said Robert H. Tichenor Jr., the department's chief of forest pest management.
"The egg mass counts that we're getting indicate the trees would be defoliated this year, and you can't put the leaves back on the trees once that happens," Tichenor said. "We're trying to get to it first."
Six years ago, gypsy moths defoliated 46,183 acres in 15 Maryland counties, including Anne Arundel. Gypsy moth infestations tend to be cyclical, experts say, and the timing is about right for another population spike.
Locally, environmentalists have narrowed down the areas most likely to be affected to 3,857 acres, mostly in Severna Park, Severn and Pasadena. Residents near areas to be sprayed began receiving letters notifying them of the plan last week.
"We know because of the kind of [hardwood] trees where the gypsy moths are likely to be a problem," Tichenor said. "We're targeting the protection areas to the places where they're likely to be a problem."
Two types of pesticide will be used. The first, Dimilin, kills insects during the molting process. The second, BT, is a bacterial spray that is considered slightly less effective on the caterpillars, but safer for use near water, where high doses can kill organisms such as crabs and fish.
The pesticides will be applied in the early morning over several weeks beginning late this month or early next month, Tichenor said. Typically, a helicopter or airplane administers the treatment from about 50 feet above the treetops.
Gerald E. Brust, an integrated pest management specialist at the Lower Eastern Shore Research and Education Center, said Dimilin and BT will affect many kinds of insects where it is applied, but not humans or other animals.
Allison Albert, program director and spokeswoman for the Severn Riverkeeper Program, questioned whether spraying unnatural substances was necessary to control the gypsy moth population.
"You can never know for sure what the effect is going to be," she said. "Spraying can affect all kinds of things, including the existence of animals who may have depended on [the gypsy moths] in the food chain."
Michael J. Raupp, an entomologist at the University of Maryland College Park, said residents shouldn't be concerned about the spraying.
"It's kind of standard operating procedure for these types of infestations, and Maryland has one of the most environmentally sensitive approaches I've seen," he said. "The way they do it, you're not going to kill a lot of beneficial insects that you'd find in those trees, and nothing in the water should be affected."