URI scientists fight invasive tree-killing beetle with beetle-killing wasp
When the invasive emerald ash borer, a beetle
native to the Far East, was found in Rhode Island in 2018, it was a sign that
most of the state’s mature ash trees were likely to die soon. Now a team of
entomologists from the University of Rhode Island is fighting the invader with
a predatory wasp from its native land in hopes that the region’s next generation
of ash trees will survive.
Lisa Tewksbury, director of the URI
Biocontrol Laboratory, and her students have been on the lookout for the
emerald ash borer for more than a decade, soon after it was first discovered in
the United States in Michigan. Now that they know it’s here, they are deploying
three species of parasitic wasp from Asia that lay their eggs in the beetle’s
eggs or larvae. When the wasp eggs hatch, the wasp larvae consume the beetle
eggs and larvae from the inside.
“The beetle doesn’t have any natural enemies in the U.S., so we’re reuniting it with its natural enemies from back where it came from,” said Tewksbury. “We’re using one organism to control another.”
The parasitic wasps have been extensively
tested to ensure that they will only prey upon emerald ash borers. They are
being raised at a federal laboratory in Michigan and shipped to Rhode Island as
pupae that are about to become adult wasps inside blocks of ash wood, which the
URI team delivers to areas where the beetle has previously been found. Once
there, the wasps will emerge and lay eggs in beetle larvae the ash trees
nearby.
Tewksbury has a permit from the U.S.
Department of Agriculture to release the wasps in targeted locations to attack
the beetle.
Ash trees make up just two percent of forests
in Rhode Island, but they are found extensively in parks and along streets
throughout the state.
“The emerald ash borer isn’t a huge concern
for our forests,” Tewksbury said. “But it will be a concern to people who have
ash trees in their yards and on their streets. There are a lot of them in
Newport and Providence.”
Last year, Tewksbury released the three
parasitic wasps in Hopkinton, near where the beetles were first discovered, and
this year they are being released in five additional locations in Burrillville
and Cumberland. The last round of releases for this year are taking place this
month, and ongoing statewide surveillance for the beetle will indicate where
additional wasp releases may take place next year.
Next year will also be the beginning of an
effort to determine if the wasps have become established and are doing their
job. Tewksbury will peel back the bark of dead and dying ash trees to see if
she can find evidence of dead beetle larvae.
“We are resigned to the fact that we’re going
to lose most of our larger ash trees, but by doing this biological control
effort we’re hoping the wasps can protect the smaller trees so we’ll have some
ash left in the future,” Tewksbury said.
Targeted biocontrol efforts such as this are
often the most cost-effective and least damaging way of fighting invasive
insects. Tewksbury’s lab is involved in testing another predatory wasp for
possible future deployment against what she expects will be the state’s next
harmful pest, the spotted lanternfly, another tree-killing invasive species
from Asia that is expected to arrive in Rhode Island in two or three years.
