Spring is in the air, and with it, the annual outbreak of dusty-winged critters that can cause extensive damage to trees and other vegetation. That's right, the dreaded Lymantria dispar dispar (LDD), formerly known as "gypsy moth," is back, and the City of Mississauga is about to fight back with aerial cavalry.

If you happen to see helicopters flying low over the 905's most populous city between May 15 and June 12, it's no cause for alarm, but part of an aerial campaign to fight LDD moth caterpillars in affected neighbourhoods.

A pair of helicopters will fly approximately 15 to 30 metres above the treetops across ten different Mississauga wards, spraying to eliminate the harmful moth caterpillars for a duration of roughly one month until mid-June.

These early-morning flights — which will happen between 5 and 7:30 a.m. — will kill the LDD caterpillars en masse, but that doesn't mean residents have to worry about toxic chemicals.

This mass mothicide is actually being carried out with a so-called “biological insecticide,” using the active ingredient Bacillus thuringiensis subspecies kurstaki (Btk) strain ABTS-351 to extinguish the lives of these creepy crawlies.

Health Canada states that Btk treatment is considered low-risk to human health and the environment, and it doesn’t even kill adult LDD moths or other butterflies, just the moth caterpillars.

But that doesn’t mean residents should be playing outside in the mist of insecticide, as Peel Public Health recommends that people stay safely indoors during and for 30 minutes after the sprays.

In addition, experts warn those in affected areas to close their windows, turn off fans and air conditioners or select the recirculate setting, bring in laundry and toys, cover up herb and vegetable gardens, pools, BBQs, lawn furniture, and to keep pets inside and wash their paws after trips outdoors.

Which is a whole mouthful of precautions for something recognized by health authorities as safe.