By: Montreal Gazette.
Has the emerald ash borer finally met its match?
In the latest attempt to halt the beetle in its bark tracks, scientists are introducing a non-stinging wasp to wage biological warfare against the nasty little critter that threatens to lay waste to entire forest canopies, one leafy ash tree at a time.
Although scientists admit not much can be done to eradicate the evasive EAB in the short-term, the City of Montreal, in collaboration with the Canadian Forestry Service and United States Department of Agriculture, has unleashed a wasp known as tetrastichus planipennisi and a pathogenic insect fungi to slow the spread of the beetle locally.
Two wasp-release sites have been set up in Montreal at the Botanical Gardens and Bois-de-Liesse nature park.
“We are just adding another mortality factor to kill the EAB,” said Dr. Maryse Barrette, a research agent with the city’s integrated pest management team. “At the forest landscape level, it might be our best chance to control the EAB, at least reduce its population in woodlots in Montreal.”
According to Canadian forestry officials, the tiny wasp parasitizes EAB larvae by boring into the bark and laying eggs on its host. The hatching wasp larvae then feed on the EAB larva, resulting in its death.
Another bio-control method involves using 200 bait-traps suspended in treetops across the city to lure the beetle to its death.
The traps are designed to “introduce a disease that could be spread through the EAB population,” said Dr. Robert Lavallée, an entomologist and research scientist with CFS.
“We put traps where the ash borer has his playground, at the top of the canopy, because it’s a sun-loving insect,” he explained.
“We try to attract the beetles inside the traps where they will be contaminated by the fungi. And when the beetles fly away from the trap, we hope they will contaminate their partner during mating. So we hope to introduce a disease into the (EAB) population.”
Despite these efforts to halt the spread of EAB, science’s intervention may come too late to save the more than 200,000 ash trees in Montreal.
“First of all, we don’t know where exactly this insect is,” Dr. Lavallée said. “Only when a tree is dying, do we know where it is. It’s under the bark, but (by then) it’s too late.”
Even the parasitoid wasp program launched three summers ago in Ontario has not halted the beetle’s destructive path so far, said Dr. Barry Lyons of the Sault Ste. Marie lab of the Canadian Forestry Service.
“So far it hasn’t been very efficient,” he said.
“Bio-control is a very long-term proposition. It’s something that takes years and years to develop. So you introduce an insect into a local area and it takes several years for its population to build up, and it has to have a chance to catch up to the host it’s trying to attack. In this case, the emerald ash borer.”
Dr. Lyons said the Americans began a wasp-release program in 2007, “and just last year they started to see significant population buildup (of wasps). So that’s seven years and they still haven’t seen any dramatic reduction in the emerald ash borer population.
“The Americans are starting to say they’re not going to be able to protect this generation of ash trees, but maybe the next generation.”
In other words, temper expectations about wiping out the beetle with bio-warfare.
“This is not the silver bullet,” Dr. Lyons said. “This is not something that is going to happen overnight. This takes a fair bit of time … This is another tool in the arsenal.
“The neat thing about biological control is that it’s sustainable. Once you release the insects, the parasitoids, they’re going to continue to do their job. And they’re going to keep spreading and attacking the emerald ash borer.”
In his 35 years with the National Forestry Service, Dr. Lyons said the EAB, which originated in Asia, “is the worst insect we’ve ever seen.”
“It’s a devastating insect that has spread incredibly fast, beyond anybody’s expectation. When it first arrived in North America in the 1990s, it took at least 10 or more years before we even discovered it. And by that time it had spread dramatically … and caused devastation.
‘We found it in Canada (near Windsor, Ont.) in 2002 for the first time, but we suspected it was here in the 1990s.”