Forest Service Combats Emerald Ash Borer With Wasps

The U.S. Forest Service has released stingless wasps along the eastern edge of Michigan's Huron-Manistee National Forests, on the state's lower peninsula, to help counteract the invasive emerald ash borer.

The release marked the first time biological measures were taken to fight the beetle inside a national forest. In July, the Forest Service received approval to release two species of parasitoid wasps, Oobius agrili and Tetrastichus planipennisi, in the national forest and on nearby private lands in Michigan's Alcona County. Environmental analyses showed that the wasps do not harm people, non-target species, or the environment.

"The emerald ash borer has caused so much damage to forests and so much loss to communities in Michigan's Lower Peninsula," said Michael T. Rains, director of the U.S. Forest Service's Northern Research Station. "Expanding the use of biological control to national forests and research on its effectiveness will contribute to more resilient forests in the future."

The tiny beetle first made its way to the U.S. in the early '90s, "presumably from solid wood packing materials or dunnage used to transport manufactured goods," according to the U.S. Forest Service. It has since spread to at least 13 states.

The Forest Service doubts the wasps can save larger ash trees, but they could reduce the beetle population enough to "curb their effect in the future."

The two wasps have different ways of preying on the beetles. Oobius finds a beetle egg and injects its own egg inside, where it will hatch, grow, and kill the host egg. Tetrastichus females lay eggs inside beetle larvae, where the wasp larvae feed and grow, eventually killing their host.

More on the emerald as borer can be read here.

Emerald Ash Borer, or Agrilus planipennis

Oobius agrili

Tetrastichus planipennisi