The allies have landed on the shores of Echo Lake.
With the help of state entomologists, nearly 15,000 Gallerucella beetles were released recently along the shoreline of this Union County park, which straddles the Westfield-Mountainside border.
Their objective: purple loosestrife, an invasive plant that when unchecked, chokes out native plant species.
On a recent Friday morning, Mark Mayer, supervising entomologist with the state Department of Agriculture's Bureau of Biological Pest Control, met with county parks naturalists to release the beetles.And as soon as the little buggers warmed up – they are transported in chilled containers – they started swarming the leaves on the nearby loosestrife like they hadn't eaten in weeks.
The Gallerucella beetles have been released in well over 100 areas in New Jersey.
"Sussex County was really bad," Mayer said, noting that conditions have improved there markedly.
The beetle was released at Echo Lake Park several years ago, but the recent dredging project to clear the lake had the unintended consequence of reducing the beetle population, Mayer said. When the lake was lowered, it is likely that many of the beetles burrowed into the exposed soil to pupate. But when the next generation hatched, they would have drowned because the water level had risen in the interim.
The recent release was to get the beetles back up to a level where they would keep the purple loosestrife in check.
"The goal is not to eradicate, but to bring it down to a tolerable level," Mayer said. "Loosestrife can grow to a height of seven feet, but it doesn't do that now because of the beetles. "
The loosestrife made its way to America in the 1800s. Ships that did not have full cargo holds would use soil for additional ballast to stabilize the boat. But when that space was needed for the return voyage, the dirt that contained the loosestrife seeds was dumped along the American shores. From there, it just started spreading inland, Mayer said.
In the mid-90s a Cornell University professor Bernd Blossey was doing research in Germany when he discovered the Gallerucella beetle and its predilection for purple loosestrife, Mayer said. After extensive testing, the federal government approved using the beetle to control the plant and at a special state Department of Agriculture facility in West Trenton, one of only a handful in the country, the beetles are raised and then transported to areas around the state where the loosestrife has gotten out of control, Mayer said.
The Union County Board of Freeholders approved dredging Echo Lake because years of silt accumulation had taken their toll, with islands being created because so much soil had settled in the upper lake. In addition to improving the water flow and deepening the lake, it also enabled the return of paddleboats, which had been a favorite pastime at the facility. The paddleboat concession reopened last month.
But it was after the dredging, however, the purple loosestrife started spreading again. So the county requested another application of the beetles, fearing that if the situation had gone unchecked, the loosestrife would have choked off the lake entirely.
The Gallerucella beetle is not the first time Union County has been on the frontlines of the biological war to control invasive species. Two years ago, in the Watchung Reservation, tiny weevils imported from China, known as Rhinoncomimus latipes, were brought in to feed on Mile-a-minute weed.
Mile-a-Minute Weed, Polygonum perfoliatum, can grow up to six inches per day, with mature plants reaching six feet, according to state plant experts, it can climb over, and shade out native plants at the edges of woods, along stream banks and roadsides.