Nasty tree-killing bagworm making comeback in Windsor

The city's manager of forestry says bagworm increasingly spotted in some areas of the city.

After first being identified in 2008 in Windsor, bagworm became a significant problem by 2013

Bill Roesel says the bags look like Christmas decorations hanging on the trees. (Tony Doucette/CBC News)

Windsor's nasty bagworm is making a bit of a comeback with sightings of the tree-crippling parasite increasing throughout the city.

Back in 2013 and 2014, the city had a major problem with bagworm, which quickly destroy evergreens by eating its needles. City staff say the bagworm is making a moderate return this year after a mild winter. 

It was also a much bigger problem two years ago, according to city forester Paul Giroux, but two cold winters kept them under control.

"When the temperatures get down to -14 to -18C for any 24 hour period during the winter it greatly reduces the amounts of active eggs for that season, which turn into female and male moths," said Giroux.

Destroyed trees

Danese D'Amore lost a blue spruce in just four weeks to the bag worm. She didn't realize she had a bagworm problem in her yard on Casgrain Drive until it was too late.

She now sees them on nearby trees as well.

D'Amore has been doing her best to kill the bagworm by boiling them, but she worries they could do much more damage, if left to thrive.

Danese D'Amore is fighting bagworm on her property. The nasty parasite has already killed one of her trees. (Dale Molnar/CBC)

"If it got into our parklands or even to a would destroy it," she said.

Bagworm is known to attack 128 species of trees, both deciduous and coniferous. It destroys evergreens by eating the needles and making an egg sack or bag which hangs from the female.

The tree, which can no longer can't make new needles or leaves, eventually dies.

First arrived in 2008

The bagworm was first found in Windsor in 2008. Surveys conducted by Ontario's Ministry of Natural Resources found the number had increased in 2011. By 2013 new infestations were observed on trees throughout the city.

Giroux attributes this year's slight increase in bagworm population to the past mild winter. He calls the latest infestation a "moderate" one, which the city is monitoring, but doesn't plan to spray for it just yet.

​Giroux says everyone should check their trees. If they find they cocoon-like bags, they should take them off and drown them in a jar with boiling water.

He says there is also a pesticide you can spray trees with called B.T. Throwing them away or stepping on them won't necessarily kill hundreds of eggs in the sack.​