Climate change, bugs, and Canadian Christmas tree health

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Digital Reporter Hailey Montgomery

Saturday, November 25, 2017, 6:52 PM - The population of a species of pest that loves to gorge on Canadian Christmas trees could get a boost from the warming of our planet.

Christmas trees are a major export in Canada. According to Statistics Canada, $78.4 million were spent on fresh-cut Canadian Christmas trees in 2015, and most of the country's trees are grown in Quebec, Nova Scotia, Ontario, British Columbia, and New Brunswick. In 2015, we exported $41 million worth of trees worldwide -- $36 million to the United States alone.

The Mindarus abietinus, commonly known as the Balsam twig aphid, is a small sap-sucking insect that favours Canadian balsam and Fraser fir trees, a popular choice for fresh-cut tree shoppers.

Courtesy of Natural Resources Canada

The aphids are a problem for the trees' aesthetics and overall health. As the pests feed, they secrete a substance which make the trees needles swell and curl. When an infestation is large, trees will grow less needles, and their shoots (fir tree branches) can experience stunted growth.

These "tree lice" lay eggs in March and April, depending on the warmth of a given season. Biologists at Quebec's Laval University wondered weather a warmer temperatures in late spring and summer would impact population density of the aphids.

"In southern Québec, the average annual temperature has increased between 0.8 °C and 1.6 °C since the 1960s, accompanied by a longer growing season for plants (Yagouti et al. 2008)," the study 2017 reads. "For the coming decades, an increase between 2.4 °C and 4.6 °C of the average annual temperature is predicted if greenhouse gas emissions continue at the current rate throughout the 21st century (Ouranos 2015)."

These warming temperatures, the research asserts, disturbs the complex life and sexual reproduction cycles of the bugs.

Carried out over two years in three commercial tree plants in southern Quebec, the study found that the species thrived on Balsam fir trees in stimulated warm temperatures, therefore causing more damage versus the colder experimental environments.

"In the following decades, increasing air temperatures brought on by climate change may benefit this species and reinforce its status as an important pest in commercial Christmas tree plantations," they said.

Source: Laval University as published in The Canadian Entomologist | Environment Canada | Michigan State University

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