Trees in southern Ontario are in danger, says U of G prof
Ash, maple, birch, willow, elm and fruit trees are all at risk in southern Ontario because of two exotic beetle species that have make their way to North America, according to University of Guelph environmental biology professor Gard Otis.
One of the pests, the Asian long-horned beetle, was recently discovered in Toronto, and it's hoped the insect can be contained to a small region of that city, said Otis. But another Asian beetle, the emerald ash borer, has already killed thousands of ash trees in the Windsor area.
Working with graduate student Nicole McKenzie, Otis is helping to detect and contain emerald ash borers before they spread across the country. "When I heard about the emerald ash borer, I saw it as a research opportunity," said Otis. "I was lucky and got linked with Canadian Forest Service researchers who are spearheading a number of projects to understand everything we can about the beetle."
Most people barely notice dead trees, let alone take the time to stop and look at what may have killed them. That's why both species went undetected for several years.
"For both these beetles, until the adults emerge and there is an exit hole in the tree or trees are dying in large numbers, there is little evidence they are infested," said Otis. "Only if you look closely for symptoms and peel back bark will you see their mark."
"The discovery of the Asian long-horned beetle in Toronto came as a huge surprise," says Otis. One of the people called to help diagnose the bug during the initial outbreak was Otis's colleague, Steve Marshall, who has overseen Guelph's insect collection since 1982.
The Canadian Food Inspection Agency (CFIA) is now co-ordinating a survey of the areas infested in Toronto. "If they get into the nearby forests along the Humber River, it's going to be really hard to stop them or to detect them," said Otis. The current development stage of the beetles is buying the CFIA some time. "Luckily the beetles are done flying for the year. The CFIA has the winter to complete the survey and figure out what to do."
There are only two ways to destroy the beetles: cut, chip and burn affected trees, or inject insecticides into the trees that kill the beetle larvae as they feed.
In contrast to the relatively slow decline of trees attacked by the Asian long-horned beetle, the emerald ash beetles in southeastern Michigan and Windsor kill ash trees very quickly. "Trees in Winsdor that were healthy in spring were dead by fall," said Otis. An estimated six to ten million trees in Michigan have died result of this beetle. Already many thousands of ash trees in Essex County have died.
One focus of Otis' research has been emerald ash borer mating behaviour. "If we knew there was a sex attractant, then it may be possible to develop lures for more efficient detection and survey," he said. "Although our observations failed to provide evidence of sex pheromones, they suggest that we may be able to use green decoys to attract beetles to sticky traps."
Left to their own devices, neither of the Asian beetels disperses very rapidly. The biggest problem is their almost instantaneous dispersal through humans moving firewood. Although Otis believes Canada is being very pro-active in its fight against these pests, he predicts that in one to two years emerald ash borers will be found throughout much of Ontario as they come across the border from heavily infested counties in Michigan and as people inadvertently transport them on firewood.
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