YES Mag: The Science Magazine for Adventurous Minds, July/August, 2010
Wasp Detectives
by Sharon Oosthoek
A tiny black-winged wasp is about to become a detective in the case of the emerald ash borer, a beetle that has killed millions of ash trees in Canada and the United States. The shiny green beetles hitched a ride from Asia about 10 years ago, hidden in wood packing materials for products shipped to North American stores. It’s the beetle baby that kills trees — larvae feed under the bark and destroy the system that transports food and water to a tree.
Luckily, researchers at Ontario’s University of Guelph found that a native wasp, Cerceris fumipennis, can detect beetle-infested areas. The wasp leaves its nest in search of prey and in as little as half an hour knows if beetles are present. That’s good news because the faster we find the emerald ash borers, the faster we can stop them. Fewer trees will have to be cut down or injected with expensive pesticides to stop the beetles’ spread.
“It’s like the wasp is Sherlock Holmes and we’re his assistant Watson,” says bug expert Philip Careless, who was a master’s student at the University of Guelph when he helped figure out the wasps make good investigators. “You have a partner — which happens to be a wasp — that is awesome at finding where these pests are that are moving into our neighborhoods to eat our trees.”
Careless, who is now a bug expert with the Canadian Food Inspection Agency, says the wasp is good at finding the beetle because it’s one of its favorite meals. Mother wasps bring the beetles back to the nest to feed their larvae. Careless knows this because he visited places known to have emerald ash borers, and then he looked for wasp nests on the nearby ground.
After the mother wasps left their nests to hunt, he put clear plastic cups over the nest entrances. When a mother returned and found her nest blocked, Careless grabbed her groceries. He found — you guessed it — emerald ash borers.
Unfortunately, the wasps kill too few emerald ash borers to stop them from spreading. That’s where humans come in. Forest managers in the U.S. are now training volunteers, including scouts and guides, to watch nests and tell them when the wasps bring back emerald ash borers. In Canada, Careless and his team will spend this summer finding out where the nests are and next year volunteers can take over.
Want to volunteer, but you’re afraid of a wasp sting? No worries. “These wasps have a stinger, but they don’t use it in defense. They use it to paralyze prey,” Careless says. “We grab them all the time when we steal their groceries and they never sting us.” Beetles, beware.