Parts of St. Vital will be sprayed from the air later this month in an effort to eradicate the latest threat to Winnipeg’s urban forest — the European gypsy moth.

About 30 people attended a public information session held May 7 at Norberry-Glenlee Community Centre. Insect control officials outlined plans to use a biological insecticide known as Btk to kill gypsy moth caterpillars in and around St. Vital Park.

Btk is a type of bacteria found naturally in soils and is the active ingredient in Foray 48B, which will be applied on three occasions approximately a week apart to coincide with caterpillar development. The spraying will take place early — between 5 and 7:30 a.m. — in an area about 230 hectares in size.

The target start date is the May long weekend or shortly afterwards, but is subject to change. Marianne Schutz of Manitoba Conservation explained that aerial spraying requires no rain and very little wind "so there is likely to be postponements."

Officials said area residents would be notified several ways, with signs going up at least 24 hours prior to each application.  People can also check the city and Manitoba Conservation websites for updates and phone numbers to call, or sign up for email or phone alerts.

Fiona Ross of Manitoba Conservation said the aerial spraying will cost approximately $55,000 and will be a collaborative effort between the province and City of Winnipeg. The program was initiated after a small number of moths and egg masses turned up in traps in the St. Vital Park area.

Btk is approved by Health Canada and is widely used in organic food production. Winnipeg already uses it to control some pest insects, and the province employed Btk to eradicate gypsy moths in two areas close by Winnipeg, La Salle and St. Germain, back in 2009.

While a few residents raised health concerns at Monday’s meeting, Schutz maintained Btk is safe for fish, birds, animals, and humans and that only gypsy moths and closely related insects (like the forest tent caterpillar) would be affected by the spraying.

"Aerial spraying is the best option for the size of the affected area," Schutz said, "and it accomplishes the objective in a safe and the most effective and efficient manner."

Since their accidental introduction to the U.S. in 1869, gypsy moths have spread to Canada and are now found in every province east of Manitoba. They have also turned up in B.C.

Gypsy moth caterpillars have voracious appetites, and large numbers of them can completely strip the leaves from a tree. Over time, this can kill trees or make them more susceptible to other pests. According to Ross, gypsy moths feed on more than 450 tree species but prefer oak, poplar, basswood and birch — all common trees in Winnipeg.

The insect control officials warned that gypsy moths, if established, could spread quickly, endangering not only our urban forests but Manitoba’s commercial and recreational woodlands as well. The province’s nursery and landscaping industry would also suffer, since federal restrictions would be imposed on plants and plant products.