City spraying to control gypsy moth infestations in municipal trees
Teviah Moro Hamilton SpectatorThursday, May 27, 2021
The city wants Hamilton residents to do their part to help save trees from a gypsy moth infestation that rural councillors say is taking their wards by storm.
“We’re not just talking about a few. We’re talking about thousands on properties,” Coun. Judi Partridge said Wednesday.
The Flamborough councillor noted the caterpillars dropping from trees carry a histamine that makes some people break out in hives.
That’s also worrying residents in Glanbrook, which is “inundated” with the hairy, spotted critters, Coun. Brenda Johnson said.
“Literally, they cannot step outside the door without worrying that their kids are going to be itching with rashes.”
But the infestations also “devastate” trees, Partridge said.
European gypsy moths, which were first detected in Ontario in the 1960s, gravitate toward the broad leaves of deciduous trees like oaks and maples.
In 2018 and 2019, the city sprayed roughly 8,770 acres of trees in Ancaster, Dundas, Flamborough and the west Mountain with a biological insecticide called BTK to protect the areas’ mature deciduous tree canopy.
Without those helicopter missions, which cost about $2.5 million, Hamilton would “likely” have a bigger problem than the “isolated areas” of infestations today, forestry manager Sam Scarlett said.
The city is tackling city-owned trees on streets and parks through truck-based spraying, nest scraping and banding — an effort that has cost about $65,000 so far, Scarlett noted.
But it’s up to residents to take care of their own trees. They can tie a band of burlap around them to prevent caterpillars that have fallen to the ground from crawling back up to feed on leaves or trap them as they make their way down.
The goal is fewer egg masses in fall and winter, which means fewer caterpillars next year, Scarlett said.
The Ministry of Natural Resources and Forestry says gypsy moth defoliation in Ontario spiked to 586,385 hectares last year from 47,203 hectares in 2019.
“We expect a continued outbreak with substantial levels of defoliation in the same areas that experienced it last year. This is mostly southern Ontario and in the Sudbury area,” ministry spokesperson Jolanta Kowalski said in an email.
Gypsy moth outbreaks tend to hit every seven to 10 years and last three to five years on average. There were major ones in 1981, 1991 and 2002, Kowalski noted.
“The previous outbreak, which peaked in 2008, was much less severe than earlier ones.”
A virus and fungus can set in when populations hit their “natural peak” during that cycle, Scarlett said. “So you will have a natural population collapse at some point.”
The Royal Botanical Gardens plans to spray insecticide from a helicopter to control infestations at its Rock Chapel Sanctuary and the south shore of Cootes Paradise.
The four early-morning sprayings this week and next will also involve BTK, which the RBG notes has no negative effects on humans, birds or bees.
The gypsy moth infestations come as the city aims to increase its urban tree cover to 30 per cent from its current estimated 21 per cent.
This year, depending on how the COVID-19 pandemic continues, the goal is to add nearly 14,500 new trees to municipal land as well as hundreds to residential property.
European gypsy moths
- Eggs can be found in the bark of trees in winter.
- They hatch in spring and larvae start eating leaves. They stop feeding in July.
- Caterpillars grow to 50 millimetres long and are dark and hairy. They have a double row of five pairs of blue spots, and a double row of six pairs of red spots.
- Male moths are light brown and slender. Females are white and heavier.
- Outbreaks happen every seven to 10 years. Trees can produce new leaves in summer, but the damage “causes significant growth loss.”
- Infections can also make trees more vulnerable to other pests, drought and other adverse conditions.
Source: Ontario Ministry of Natural Resources and Forestry
Teviah Moro is a Hamilton-based reporter at The Spectator. Reach him via email: email@example.com