--Beetles fight pesky plant Battle: Loosestrife is crowding out native Maryland plants, and the insects might be the only way to control its spread.
By A Sun Staff Writer
June 19, 2003
Armed with 10,000 chilled beetles in a foam cooler, Dick Bean arrived at a marshy, wooded tract near the Anacostia River yesterday to fire the latest salvo in Maryland's war on invasive species.
Bean, an energetic entomologist with the state Department of Agriculture, quickly found the target - a stand of purple loosestrife, an invasive, flowering plant that is crowding out native vegetation in fields and gardens in 30 states across the country.
He and colleague Robert Trumbule unsealed the cooler, revealing four cardboard cartons, each containing 2,500 Galerucella beetles that had spent the night in the fridge to stay lethargic until it was time to go to work.
Bean cut a sheet of white cloth from a bolt of mesh fabric, producing a screen that looked like a wedding veil. Then, he and Trumbule spent two hours enshrouding a dozen stalks of the enemy plant and stapling the veils shut.
"Here we go," Bean said as he released a swarm of beetles at the base of one of the plants. "You guys do your stuff."
Without the shroud, the four-winged insects might fly away, heading toward sunlight. But with the shroud, Bean hopes, the beetles will cling to the loosestrife, establish colonies on the marshy Prince George's County field and devour one of Maryland's most threatening pests.
The loosestrife's affinity for marshy areas is the reason Bean chose this area between the Baltimore-Washington Parkway and the banks of the Anacostia when he began the experiment three years ago.
How the loosestrife arrived at this site "is anybody's guess," Trumule said. "It could be seeds were washed down here from the highway."
But it poses a threat to areas downriver because its seeds can be spread by the waterway. "You're not eliminating the plant, you're just controlling its spread," Bean said.
Bean dutifully records the progress made by the beetles each year, but he said it can take up to five years for a colony to become established. "It's not something that just happens. Ninety-eight percent of these beetles are going to die," he said.
Entomologists in about 30 states have released the same Galerucella beetles in an effort to kill Lythrum salicaria, as the loosestrife is officially known. Although Galerucella is not native to most of those areas, including Maryland, federal officials approved the bug's use in 1992 because it lives for only a year and likes to eat only one thing - the loosestrife.
Bean's hit squad of bugs came from a lab in Niles, Mich., operated by the U.S. Animal Plant Health Inspection Service, a federal agency charged with keeping invasive pests out of the country. He said extensive tests prove the beetles pose no danger to other plants or wildlife.
"This is probably the most extensively tested exotic species ever introduced into a habitat," Bean said.
The loosestrife arrived in the United States in the 1830s, when ships from Eurasia dumped seed-contaminated ballast at East Coast seaports. The plant spread by way of canals, rivers and streams. Like other weeds, it takes advantage of soil disturbed when land is cleared for development.
Until a few years ago, Bean said, loosestrife was sold at garden centers and used by beekeepers because the nectar from its flowers feeds honeybees. It's not enough of a threat to make state or federal noxious pest lists - which would require an outright ban on its use or sale.
"It isn't that bad yet and hopefully it won't get that bad," Bean said. But it is an invader, crowding out native grasses and creating a bland habitat in woods and marshes once rich in native plants.
Many non-native plants have thrived for centuries in Maryland without damaging crops and other vegetation - including some of the region's most productive food crops, according to Bean and other experts. But some intruders take over yards and roadsides, spreading so many seeds that they crowd out competitors.
"The problem is they take over and they alter a habitat, so that there's no room for native species," said Jonathan McKnight, a state Department of Natural Resources wildlife biologist.
McKnight said the mute swan, nutria and zebra mussel are examples of other invasive species that threaten state waterways.
The mute swan's appetite for aquatic grasses prompted the state to begin a program to shoot up to 1,500 of the aggressive birds this spring. That, in turn, prompted a lawsuit from animal-rights activists that persuaded the state to stop the shooting - at least temporarily.
The state also is trying to trap nutria, large rodents that are infesting the Chesapeake Bay and local waterways. And it's exploring ways to contain the anticipated arrival of the zebra mussel, which is likely to work its way south from New York.
The mute swans were originally imported to decorate zoos, parks and large estates, while the nutria were brought in by entrepreneurs hoping to create a market for its fur. Scientists believe the zebra mussel arrived in ballast water from ships that had visited Asia.
All three have no predators to keep populations in check and are among dozens of pests listed on a Web site established by the Maryland Invasive Species Council, a group of state agency representatives and volunteers. It's available at www.mdinvasive sp.org.