‘Army worms’ to face aerial assault

While the forest tent caterpillar, commonly referred to as the “army worm,” is marching a bit behind schedule this summer, they’ll face a greater threat with an increase in numbers of their natural enemies—the “friendly fly.”
Native to Northern Ontario and resembling a large housefly, this parasitic insect has evolved as a natural control for the forest tent caterpillar, Mark Breon, a forestry health technician with the Ministry of Natural Resources, said yesterday.
“These flies may, for a short time, become a nuisance as the population increases,” he remarked.
“The friendly fly population becomes extremely abundant just as the forest tent caterpillar outbreak is at its peak,” he added. “The fly will likely disappear around the end of July when the caterpillar finishes cocooning.”
Friendly flies do not bite or cause harm, but they can become annoying, landing on automobiles, houses, or people—hence the name “friendly fly,” noted Breon.
The fly will help decrease next year’s army worm population by laying maggots on the caterpillar’s cocoon. The maggots then attack and paralyze the caterpillar larva or pupa, killing it.
This is effective in curbing the population because the moth stage is when the worms mate, lay eggs, and die.
What’s more, those who detest the creepy crawlies will be happy to know the population appears to be in a downturn.
“As of our last egg count [in the fall], there were fewer egg bands counted, meaning there were fewer moths to lay them,” said Breon. “It appears the population’s going down.
“You may even see some areas where there’s no defoliation.”
While most residents have encountered relatively fewer worms so far this summer, the local track record isn’t so good. 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.

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