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But despite die-offs, some of the plant-eating insects are still hanging on. “I found them yesterday on a climbing rose in our backyard,” says one resident.
While the beetles are not entirely gone from Portland, Oregon’s Sellwood-Moreland neighborhood, they have begun to die.
“They’ve dramatically dropped off and they’re not anywhere close to where they were last week,” Tim Butler, who manages the Oregon Department of Agriculture’s noxious weed control program, said during an interview on Monday. “They can’t sustain themselves.”
The insects were released as part of a government “biocontrol” initiative meant to combat an invasive weed in a wildlife refuge that is located in the neighborhood. In past years the beetles have struggled to survive in the refuge mainly due to flooding patterns in wetland areas, but their numbers surged this summer and spring amid unusually warm and dry weather.
After devouring vast amounts of purple loosestrife, the plant they were supposed to eat, the insects began swarming into Sellwood-Moreland around Aug. 9. There they helped themselves to tree leaves, shrubs and garden plants, while also grossing out and agitating residents.
“At least you can walk outside without having scores of beetles cling to your body, clothes and hair,” Barbara Bernstein, a Sellwood-Moreland resident, said in an email on Monday.
When she spoke with Route Fifty last week, Bernstein described the beetle situation as akin to a “biblical plague.” Though the number of insects in neighborhood has declined, Bernstein made clear that there were still hungry beetles around.
“Now that they've eaten through all the crepe myrtles and many varieties roses in the neighborhood they've moved on to birches and understory plants,” she said. “I found them yesterday on a climbing rose in our backyard, which they hadn't touched before.”
The Oregon Department of Agriculture predicted last week that the beetles would begin die-off within a few days. Butler said that based on monitoring, and feedback from area residents, that prediction seemed to be holding true.
Without abundant loosestrife, he said, “they just didn’t have a food source.”
This year’s upswing in the leaf beetle population was attributed to a number of environmental factors that favored the insects. The entire state of Oregon is currently experiencing drought conditions and water levels were low in the Oaks Bottom Wildlife Refuge where the beetles were released. The refuge is situated on the eastern bank of the Willamette River.
“This was a pretty unique situation,” Butler said. “It really wasn’t anticipated that this would be a major issue, that they would build up that fast.”
He described the feeding that had taken place in Sellwood-Moreland as unfortunate.
“There’s no doubt that there are some rose bushes that were skeletonized from the feeding,” he said. Crepe myrtle trees and pomegranate plants were among the other damaged plants.
But Butler added: “It’s not like the neighborhoods are denuded.”
He also pointed out that the purple loosestrife in the wildlife refuge had been hard-hit, which is a good thing. “Hopefully this will lead to a more fully functioning wetland ecosystem in Oaks Bottom, and that was the intent all along,” he said.
Left unchecked, purple loosestrife can crowd out native plants, and hurt wildlife habitat. Oregon’s department of agriculture has said the weed has the potential to cost the state millions of dollars in economic damage. The leaf beetle is seen as a way to control the invasive plant without herbicides. As for ripping the loosestrife out by hand, Butler said that wouldn’t be feasible in a large area.
The Oregon Department of Agriculture has overseen leaf beetle biocontrol programs since the 1990s. But the actual release of the insects in Oaks Bottom involved Portland Parks and Recreation and the U.S. Department of Agriculture, according to Butler.
Bernstein, the Sellwood-Moreland resident, said that she’d seen recent evidence that the beetles had also eaten plants in Oaks Bottom aside from loosestrife.
There are no immediate plans to introduce any more of the insects at the refuge. And Butler called the chances of another off-target feeding happening next year “pretty slim.”
Going forward, he believes an equilibrium will emerge between the amount of purple loosestrife and the number of the insects. “They will balance out,” Butler said. He added: “No matter what you do in an integrated weed management system there’s still an element of risk.”
Bill Lucia is a Reporter for Government Executive’s Route Fifty.
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