Forest infestations explode, climate change blamed

By Sheilla Jones

Warmer than usual winters due to climate change can make life on the prairies a little less taxing, but the warmer weather linked to climate change is also making life easier for insects attacking trees.

This summer, southern Manitoba has seen significant outbreaks of Jack pine budworm in the Interlake and north of Grand Rapids.

“The Jack pine budworm just exploded this year,” said Kyla Maslaniec, a pest management biologist with Sustainable Development forestry branch. “We think is it possibly related to having two mild winters.”

Maslaniec said the cycles of Jack pine budworm typically last from 3-5 years.

“Budworm can disappear just as quickly as it appears. We’ve been expecting an infestation. We haven’t had an outbreak since the 1980s.”

The budworm larvae feed on the needles and can be identified by partially chewed needles and clumps of accumulated spun silk. Almost all the needles in the upper crown may be consumed, resulting in top kill. Multiple years of defoliation can kill off trees in as little as two or three years.

Gypsy moths strike Lee River area

The Manitoba forestry department has been working to prevent breeding populations of the invasive gypsy moth from establishing in the province. In 2009, breeding populations were detected in St. Germain and La Salle, and were successfully eradicated through aerial spraying of Bacillus thuringiensis kurstaki, a biological insecticide.

This summer, the department tackled an infestation in eastern Manitoba near Lac du Bonnet.

“We have hopefully eradicated a population around Lee River,” said Maslaniec. “We’ve been conducting mass trapping to disrupt breeding, and so far, no egg masses have been detected.”

In 2012, the province and the City of Winnipeg conducted aerial spraying and successfully eradicated an outbreak of the gypsy moth in the St. Vital area.

Sawyer beetles attacking live trees

The fall-out from the snowstorm in October 2013 is still being felt in southeastern Manitoba, when heavy snow and winds took down large swaths of forested area. The deadfall has produced a massive infestation of sawyer beetles.

“When there’s such a build-up of deadfall,” said Maslaniec, “you get a lot of sawyer beetles. Now, they’re even attacking live trees.”

Sawyer beetles lay their eggs in recently killed trees, the grubs tunnel inside the tree, and then emerge as adults two years later.

The problem is affecting about 3.2 million hectares of forest, in southeastern Manitoba and northwestern Ontario around Kenora that was hit by the 2013 storm and by a number of forest fires.

Sawflies and gypsy moths

Maslaniec said other insects have been unusually active this past summer, including the forest tent caterpillar and the yellow-headed sawfly.

“The forest tent caterpillar problem was right across southern Manitoba this year. They tend to prefer aspen trees, but for some reason, this year in Brandon they were going after ash trees.”

She said that the yellow-headed sawfly is generally around, but that there’s been an uptick this year in the number of reports.

The solution to most of the tree infestation, she said, is a cold winter.

“We’re concerned about weather issues. The forest tent caterpillar, for instance, should be declining, but with the warm weather, it’s not. Climate change is certainly a factor.”

The Manitoba Woodlot, Issue 117