Fox's announcement follows the recommendations of a scientific panel that met two weeks ago and advocated using rotenone, a root-based substance that disrupts the flow of oxygen to the gills and kills fish within hours.
Department of Natural Resources officials and panelists said they expected Fox to follow the panel's recommendation and act quickly to rid the pond of the northern snakeheads, voracious predators from China's Yangtze River that can slither on their fins, breathe air and survive on land for three days.
Fox declined to say exactly when the pond would be poisoned, but said he expected the process to begin within a few days, depending on when the area next has a stretch of clear days. Herbicides work best in warm, dry weather.
"We're waiting for a long string of nonrainy days," DNR spokeswoman Heather Lynch said.
The sharp-toothed, torpedo-shaped predator surfaced in June in a pond behind Dunkin' Donuts on Route 3. The infestation began when a local man dumped two snakeheads, one male and one female, in the pond after they outgrew their aquarium. Now the pond is loaded with juvenile fish, and scientists worry they could wriggle into the Little Patuxent River 75 yards away.
Although mindful of the urgency of the problem, Fox said he wanted to weigh all the factors before making a decision. The secretary, who has more than 20 years' experience as an environmental activist and government administrator, spent much of the past two weeks talking with scientists about the chemicals and their safety.
"I wanted to be very confident that we understood the ramifications of adding these chemicals to the pond," he said. "I'm very confident now that the chemicals we are using are going to be safe."
The first step is for DNR's fisheries service to spray herbicides to eliminate aquatic vegetation so the pond's oxygen levels drop and the rotenone works better. Killing the vegetation will eliminate potential hiding places for snakeheads.
About one to two weeks after scientists apply the herbicide, fisheries staff will spray the rotenone. DNR officials will remove dead fish daily, but said expect unpleasant odors from decaying material at the site should be expected. Although the poison dissipates quickly and is not harmful to humans, workers will wear respirators while applying it from boats.
Lynch said Fox approached the problem scientifically, taking his staff to tour the pond last week and looking at soil and water levels.
"He wanted to look at the site and really weigh the options," she said.
Fox said the vegetation will grow back within a few weeks, and the pond will be restocked by next spring.
"By this time next year, we will have a thriving and healthy pond that is rid of snakeheads," he said.