Gypsy moth caterpillar outbreak plaguing Simcoe County and beyond, but a virus could soon do them all in

Too late for aerial spray, anti-histamine should help with rashes

Anyone who has stepped outside has probably seen them: gypsy moth caterpillars are blanketing Simcoe County in one of the worst outbreaks of the bugs in recent years.

“We’re getting reports from all over the county; from the north, and Tiny, Adjala-Tosoronto, Barrie,” Graeme Davis, forester for the County of Simcoe, told Barrie 360 over the phone. “And it’s not just within the county, by the way, certainly reports of pretty widespread impacts across South and Central Ontario this year. But we were anticipating that there would be a fairly severe hatch this spring. And that’s definitely what we’re seeing.”

Davis says experts can estimate what kind of population to expect based on numbers from the year before. “That’s how we can generally anticipate what we’re going to see for the following season,” he added. “This European gypsy moth, just as the name implies, is not native to Ontario and was actually introduced in this part of the world in the 1980s. We started a really significant infestation in around 1990-92 and that’s actually the last time that we saw something similar to what we’re experiencing now.”

Now that they’re here, what can we do about them? Davis says, at this point, not much. “I certainly recognize it’s a pretty significant nuisance for folks this year. And it is unfortunate, especially with everybody wanting to get outside and enjoy this nice weather. But this too will pass and the vast majority of trees will recover from this.” Davis suggests property owners use gloves to pick the insects off one-by-one or spray a soapy solution onto affected trees. He says wrapping burlap or other fabric around the trunk of the affected tree can help collect the insects for removal. “What that does is provide a space for the caterpillars. They’ll tend to climb down and look for a shady spot during the heat of the day. They’ll climb down the base of the tree and underneath that flap of cloth or burlap. And using some gloves, you can scrape those off and drop them into some soapy water to control numbers that way.” Davis points it is the responsibility of the property owner to deal with gypsy moths or the like.

A petition was created to have the city of Barrie perform an aerial spray to control the gypsy moth population. Unfortunately, that petition was started too late. “Staff did look into the option of aerial spraying, however, it takes months of public consultation, public notices, environmental approvals and flight approvals along with the tendering process to get a company in place,” said Kevin Rankin, the city’s Supervisor of Urban Forestry. “For BTK applications (aerial pesticide) to be effective, precise timing is essential. BTK must be applied after larvae hatch and begin feeding but before larval development beyond the second instar stage, as in this week, no later.” Rankin points out the cost of aerial spraying would outweigh the short-term benefits.

Davis agrees, pointing out the entire population might soon do itself in, and in a method not unfamiliar to us humans. “The general level of gypsy moth that we’re seeing right now will collapse and will do so naturally. There’s typically a virus and/or a fungus that will play a role there,” he said. “It’s typically the virus that essentially will become more predominant within the population of caterpillars as the population gets larger, and that virus will grow and spread. And it will essentially kill the caterpillars before they reach maturity.”

Until then, the insects will continue to play a nuisance in the region, and may even cause adverse reactions to some; there have been reports of people developing a rash after coming into contact with these insects. “It’s really just like a histamine-type reaction,” concluded Davis. “This isn’t a poisonous insect. Certainly, if these insects land on them, people can experience a rash.” An anti-histamine should remedy the symptoms.

Feature image courtesy Invasive Species Centre via Twitter