VIDEO

Predatory beetles fight to save Maine’s hemlocks

Posted June 10, 2015, at 3:23 p.m.
Last modified June 10, 2015, at 4:41 p.m.

An invasive insect called the hemlock woolly adelgid has been spreading up the Maine coast since first discovered in the state more than a decade ago. As its name suggests, the pest infests hemlock trees. It saps them of moisture and nutrients, causing the trees to become sick and, under certain conditions, die.

Paul Dumdey, a private woodlot owner in Woolwich, knew it only was a matter of time before he found the foreign pest in his forest. Last fall, he harvested a large hemlock tree from his 150-acre woodlot, and at the top of the tree he found what he had been dreading: hemlock woolly adelgids.

Covered with a white, waxy, wool-like material, they looked like tiny cotton balls clinging to the undersides of the branches.

“That really left me with a sinking feeling in my stomach,” Dumdey said.

A member of the Small Woodland Owners Association of Maine, or SWOAM, Dumdey learned about the relatively new pest at a number of SWOAM presentations and knew who to call for advice.

Allison Kanoti of the Maine Forest Service has been working with other forest entomologists throughout New England to manage the spread and damage caused by hemlock wooly adelgid for several years.

Originally from Japan, the hemlock woolly adelgid inadvertently was shipped to Maine from Connecticut on untreated nursery stock in 1999. By 2003, a natural spread of hemlock woolly adelgid was detected in forests in the southern Maine towns of Kittery and York. The pest has since spread up the coast as far as Camden.

“We’ve had detections on planted trees all the way out to Lubec and all the way up to Bangor,” Kanoti said. “But in the forest, so far, its just limited to basically Knox County south and just coastal counties.”

Since 2004, state entomologists have been fighting the hemlock woolly adelgid with predator beetles known as Sasajiscymnus tsugae. Related to ladybugs, these tiny black beetles feed specifically on hemlock woolly adelgid.

“Right now, it’s the best tool that we have for management in the forest of hemlock woolly adelgid,” Kanoti said.

Dumdey called Kanoti and told her about the hemlock woolly adelgid he found on his trees. Together, they decided to take action. Located on the inland edge of the pest’s known range, the Woolwich woodlot was a prime location to release the predatory lady beetle.

On June 5, Kanoti and a group of other Maine Forest Service staff members hiked half a mile into Dumdey’s Woolwich woodlot to released 3,600 of the predatory beetles.

Dumdey and his dog, Annie, tagged along for the event. Upon reaching an infested hemlock tree, Kanoti handed him a container full of the tiny black beetles.

“A lot of times you can sweep them out onto the foliage of the tree,” she told Dumdey. “But sometimes they need a little extra coaxing, and a paintbrush is a good way to move insects without squishing them.”

To the naked eye, the black lady beetles appear rather plain; but under a microscope, you can see they are covered with tiny golden hairs, Kanoti said.

“This particular species is important in the predator complex in Japan, where adelgids come from,” she explained. “They have chewing mouthparts. So they eat eggs and they eat larvae and adults.”

Since 2004, the Maine Forest Service has released more than 95,000 of these predatory beetles at select locations throughout Cumberland, Lincoln, Sagadahoc and York counties.

The beetles are purchased from a small lab in Pennsylvania for $2 per beetle, Kanoti said. Funding for these releases come from a variety of sources, but the Woolwich release in particular was funded by a U.S. Forest Service grant for the management of hemlock health.

While the biological-control effort isn’t expected to eradicate the infestation, biologists believe it will reduce the hemlock woolly adelgid population, which in turn will minimize the damage done to the trees.

“We have good evidence that in southern New England and New Jersey, [lady beetle] release sites fare better than nonrelease sites,” Kanoti said.

In Woolwich, hundreds of beetles scuttled out of the container and onto the branches of the infested hemlock tree.

“We call them ‘solar powered.’ They’re going to go where it’s sunny and there’s food. So even though there’s not a lot of adelgid down below, we’re confident they’re going to find the food they need up above,” Kanoti said, motioning to the evergreen canopy overhead.

“We don’t know how long it will take for lady beetles to have enough of an impact to protect the health of the hemlock trees,” she added. “Our hope is, in the long term, they’re going to provide some protection against damage from the pest and help the trees survive the damage that the pest causes.”

To learn about hemlock woolly adelgid, visit Maine maine.gov/dacf/mfs/forest_health/insects/hemlock_woolly_adelgid.htm.

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