While many district residents battled flood waters last week, the torrential rains hasn’t dampened the progressive march of forest tent caterpillars, commonly referred to here as “army worms.”
“They’re a little behind schedule but that’s pretty much what we expected,” said Mark Breon, a forestry health technician with the Ministry of Natural Resources.
“It was mostly rain, not cold temperatures. And we found in the past, that’s the only thing would really affect their numbers at this point,” he added.
Breon, who studies insects across the region, said most recent reports are showing the first signs of the caterpillars’ appearance, including the Fort Frances area.
“They’re very small, maybe one cm long right now,” he remarked. “In the Kenora area, I’ve started to see scattered pockets of defoliation.
“By the end of June, they should be finished their feeding period and into their moth stage by early July. So they’re clearly a little late this year,” added Breon.
Mature larvae, which usually reach this stage by mid-June, can be recognized as 4.5-5.5 cm long caterpillars, with white keyhole or footprint-shaped markings down their back, and blue bands and brown hairs on either side of their bodies.
They then spin cocoons, from which emerges moths after a 10-day incubation period. This usually happens in early July, after which they live only for a few days during which they mates, lay eggs, and die.
These eggs can be seen in bands around twigs, each of which contains 150-200 eggs. Within three weeks, a larvae forms in each egg, but then remains dormant until the following spring.
While some residents dread seeing the worms, which besides being unsightly can make a thorough mess of their hardwood trees, Breon said there might be some good news.
“As of our last egg count [in the fall], there were fewer egg bands counted, meaning there were fewer moths to lay them,” he remarked.
“It appears the population’s going down. You may even see some areas where there’s no defoliation,” he said.
Fort Frances District saw the most damage of anywhere else in Northwestern Ontario last year at 2,351,938 hectares of foliage. In 2000, the worms consumed 1,832,570 ha. while in 1999, they destroyed just 93,339 ha.
The region as a whole saw almost five times more foliage consumed than northeastern Ontario—and 30 times as much as in south-central Ontario.
