News Centre

News Releases

First Phase of LDD Moth aerial spray program to begin next week

HAMILTON, ON – Beginning on Tuesday, May 24, the City will begin its aerial spray program to address the areas where significant LDD Moth (previously referred to as Gypsy Moth) populations are located in Hamilton.

The first of two organic biological insecticide (Btk) applications will begin on Tuesday, with the second application occurring the following week. Low flying helicopters will begin applying Btk to wooded properties and residential streets in east and west Hamilton, Ancaster, Dundas and Waterdown, to help manage the infestation on City-owned properties. Residents living within the spray area have been notified of the spray program.

There may be minor traffic delays around the spray areas between the hours of 5 am and 7:30 am during the spray dates.

An interactive map of the treatment area, along with exact dates and times for the aerial spray, which are weather dependent, are available at

According to Health Canada, members of the public are unlikely to experience any symptoms if inadvertently exposed to Btk spray, and no special precautions are necessary or required. However, individuals who have concerns should take reasonable precautions to avoid exposure during a spray program in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued. They can also reduce exposure by staying indoors with windows and doors shut during the spray period if spraying is taking place in their area, although this is not required by health officials.

Btk specifically targets LDD and other caterpillars and contains a naturally occurring bacterium that when ingested kills the caterpillar within one to two days. The aerial spray will not eradicate the pest entirely, rather, it will regulate population size. The product has minimal environmental impact on other insects, pets, other mammals or bees.

Quick Facts:

  • As part of the City of Hamilton’s commitment to diversity and inclusion, the City has replaced the name Gypsy Moth with its Latin name, Lymantria dispar dispar (LDD) in its communications to help educate residents about the invasive pest while remaining sensitive to the negative connotations associated with its common name.
  • In 2008, Council approved a by-law that directs control programs be implemented if populations of LDD Moth are above an identified treatment threshold. Monitoring completed in the fall of 2021 noted high populations of LDD Moth, which exceed this threshold.
  • LDD moth larvae or caterpillars will feed on tree leaves and in some cases evergreen needles. If the larvae population is too high, they will defoliate entire tree canopies and forests in a short amount of time.
  • Repeated consecutive defoliation of trees of three years or more has the potential to kill trees and cause a long-term negative impact to the urban forest.
  • The City of Hamilton last conducted a similar aerial spray program in 2019. Program frequency is determined as part of the City’s Integrated Pest Management (IPM) program.

For further information, including spray dates when available, please call 905-546-CITY (2489) or 1-877-446-2424 toll free.

Additional Resources: