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Invasion imminent

The good news is the most ravaging effects of the gypsy moth on trees is not likely to be seen in the Sault and Algoma area (even though the moth is already here).

The good news is the most ravaging effects of the gypsy moth on trees is not likely to be seen in the Sault and Algoma area (even though the moth is already here).

However, the bad news is a wave of forest tent caterpillars (pictured) is expected soon.

That from Dr. Taylor Scarr, a Sault-based forest entomologist with the Ontario Ministry of Natural Resources.

Swarms of the unsightly pests tend to manifest themselves every 12 years or so, the last outbreak in our area being in 2002.

“The forest tent caterpillar is due to return to Sault Ste. Marie over the next couple of years, and has already caused some havoc in northwestern Ontario,” Scarr told

“They hang around for three years at a time, then they collapse because of a virus,” Scarr said. 

“It’s similar to the gypsy moth but feeds only on hardwood, maples, birch…there can be severe defoliation (loss of leaves), up to 75 percent or more, while not necessarily killing trees,” Scarr said.

Trees that get nibbled on by the forest tent caterpillar usually refoliate with no lasting damage.

Still, if you want to get the creatures off your trees, Scarr recommends use of the biological insecticide BTK.

This substance can be purchased at hardware stores or garden centres.

If you have trees spread over a large area, such as a farm (and if you have the money), you may hire an aerial spray company to address the problem, Scarr said.

The easiest way to address the caterpillars is to manually remove egg bands, or let other creatures such as birds and spiders get at them.

A unique type of fly, known as the friendly, large flesh fly, increases in number as the forest tent caterpillar does, and these flies consume a large quantity of the caterpillars, Scarr said.

In regards to the gypsy moth, Scarr said “In the U.S. (in northeastern Minnesota’s Cook and Lake counties, specifically) they’re doing this slow-the-spread program by using pheromone trap surveys to find the insect, and then they are spraying with BTK, a bacterial insecticide, and they spray pheromones as well, which helps keep males away from the females.”

“Those counties have been officially declared as infested with gypsy moth which tells us that the insect is well-established there and it’s beyond eradication, and they’re hoping it won’t spread further.”

Visitors to that area of Minnesota should make sure they are not transporting any gypsy moth egg masses on their outdoor equipment, vehicles or firewood.

The egg masses are about the size of a dime or a quarter and have a brown, chamois-like hairy covering.

Failure to spot and remove them means visitors could be transporting them anywhere, including northern Ontario.

The gypsy moth is, in fact, already here in the Sault and Algoma area, Scarr said, but visual inspection by people of their outdoor equipment, vehicles or firewood before leaving Minnesota will prevent more from being transported here.

The gypsy moth, which feeds on 400 species of trees, especially oak, has been in our area since the late 1980s, Scarr said.

“It’s never done particularly well here, we see it, but in most cases there hasn’t been severe defoliation, probably the cold winters have kept the population low.”

The main concern for the MNR in regards to invasive species, Scarr said, is the ongoing battle with the emerald ash borer, an invasive species from China.

Damage done to local trees by the emerald ash borer can be seen especially along Great Northern Road, near the YMCA on McNabb Street, the Churchill Plaza area, the Shannon Road area and along the waterfront on Foster Drive.

Work continues on testing of new traps, lures and insecticides to use in the fight against the emerald ash borer.