Using slingshots to battle invasives?

Close up of Eastern Hemlock tree branch without visible invasive insects Sleepyhobbit/shutterstock

Canadian Forest Service biologist Jeff Fidgen loads a racquetball into his slingshot, aims at a towering hemlock tree, and—thwack—strikes a blow against one of Canada’s newest tree-killing invasives.

His target is the hemlock woolly adelgid (pronounced “Adele-jid”), a sap-sucking insect named for its fuzzy, protective “wool”. The Japanese import has killed swaths of hemlocks in the U.S. Now it’s attacking trees in southwestern Nova Scotia and isolated pockets of Ontario’s Niagara Region.

The eastern hemlock is what Fidgen calls an “ecological foundation species,” sheltering dozens of other species including brook trout, migratory warblers, barred owls, deer, even salamanders and spiders. If the adelgid’s expansion continues, it “has the potential to kill most of our hemlocks, particularly when we look at the added impact of climate change.”

“It’s like cancer or any disease: the sooner you detect it, the more options you have for managing it,” he adds. “If we can find infestations when they’re very small, we might be able to remove them” by tree cutting or pesticides. (Biological controls, including predatory insects and fungi, are in the research stage.)

But how do you find a few tiny wool balls on the newest, most succulent branch tips, 20 or 30 metres above the ground?

That’s where the slingshot comes in. Originally made to fling tennis balls for dogs, Fidgen uses it to launch Velcro-covered racquetballs into the canopy. As the sphere pinballs through the foliage, the Velcro snags tell-tale signs of wool. When Fidgen retrieves a wool-covered ball, he has proof of the adelgid. See the technique in action:

The concept seems simple, but it took heavy science (and tired arms) to make it work. Backed by researchers from Sault Ste. Marie’s Great Lakes Forestry Centre and Cornell University in the U.S., Fidgen fired thousands of racquetballs to perfect “ball sampling.” Key changes included switching to red or pink balls (easier to find than the standard blue) and filling the ball with wooden beads (to add heft and reduce bouncing).

“I can see this being a tool that anyone can use,” says Fidgen, who demonstrates the slingshot technique in a new video. “The cottage owner with a few trees on the property may want to do this.” Sightings should be reported to the Invasive Species Centre.

As invasive insect surveys go, it’s quick, efficient, “and a tremendous amount of fun,” he adds. “I always begin my presentations with ‘Yes, I get paid to do this.’”

Read more: How to protect your trees from invasive species


Featured Video