According to Mother Nature’s clock, northwestern Ontario is due for an outbreak of the forest tent caterpillar, says a provincial expert who studies the bug.

It’s been 10 years since the last large outbreak in the region which, according to the normal cycle of the insect, makes the area due for another infestation, said Taylor Scarr, an entomologist with Ministry of Natural Resources.

Forest tent caterpillars are hairy insects with large blue-coloured stripes on the abdomen and a line of white keyhole-shaped marks down their backs. In northern Ontario they thrive on hardwood vegetation like birch, aspen, poplar and willow trees.

When the caterpillars get really large, Scarr said you’ll see them everywhere – including on the roads.

"In some cases there are reports of [the caterpillars] being so numerous that the Ministry of Transportation actually has to apply sand on some highway corners because the roads are getting so greasy with squished caterpillars," Scarr said.

An outbreak will also mean a spike the parasitic "friendly fly," which resembles a house fly and tracks the tent caterpillar.  

Mapping the infestation

Within the next few weeks, the Ministry of Natural Resources will be doing aerial mapping in an attempt to determine the size of this year’s infestation.

According to the ministry, about 12,000 hectares of forest have already experienced moderate to extreme defoliation in the Kenora, Sioux Lookout, and northern Greenstone areas.

Personal property owners can’t do much to prepare either, Scarr said. Potential short-term solutions include spraying woodlots or putting sticky bands on the bottom of trees to stop caterpillars from climbing up.

For the most part, he says trees survive the impact, and don’t usually die unless there’s another stressor like drought added into nature’s mix.

While this year marks the start of the caterpillar outbreak, the situation will continue to expand in the coming summer seasons.

"Right now it’s in the tens of thousands of hectares," Scarr said. "It will probably get into the millions of hectares over the next few years … and then spreading east into northeastern and perhaps southern Ontario as well."