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2017 RCGS Independent Research Grant Recipient

Christopher Greyson-Gaito
The potential of mixed forests to reduce the severity of spruce budworm outbreaks in Atlantic Canada

Researchers looking at the samples collected from a malaise trap. A malaise trap catches flying insects. They are looking for wasps and flies that attack spruce budworm, collectively called parasitoids. (Photo: Rosanna Lamb (NRCan/RNCan)

Researchers initially realized the potential of mixed forests for reducing the severity of spruce budworm outbreaks when they observed that after an outbreak more healthy balsam firs remained in mixed forests than in purely softwood forests. Researchers found more parasitoids in mixed forests and fewer spruce budworms.

From anecdotal evidence, researchers know that these parasitoids can attack other caterpillar species on hardwood trees, as well as attacking spruce budworm on softwood trees. Researchers hypothesize that parasitoids attack caterpillars on hardwoods when spruce budworms are in low supply, but will attack spruce budworms on softwoods when they are in abundance. Since mixed forests contain greater numbers of other caterpillars on hardwoods, mixed forests contain more parasitoids, which attack spruce budworms and reduce their number.

This study will use naturally occurring, non-radioactive carbon isotopes to establish whether parasitoids are attacking caterpillars from hardwoods versus spruce budworms from softwoods, while spruce budworm populations are peaking and declining. If this hypothesis is correct, action could be taken to increase the acreage of mixed forests in Atlantic Canada, potentially preventing massive spruce budworm outbreaks.


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