LDD Moth Control

Municipal LDD moth control program includes UTM campus

LDD moth on green leafThe City of Mississauga’s 2022 Lymantria dispar dispar (LDD) moth control program will target a portion of the U of T Mississauga campus this spring. Between mid-May to mid-June, depending on weather conditions, the emergence of the LDD caterpillars and leaf development, helicopters will fly at low altitude and release a pesticide over 2,091 hectares of the city, including 41-hectares of the campus.

UPDATE: The UTM campus is tentatively scheduled to be sprayed on Sunday, June 5 at 5 a.m. (weather permitting)

If left unmanaged, elevated LDD population levels will lead to defoliation of the City’s tree canopy, which can cause certain trees to become more susceptible to disease and weather events like ice storms. LDD moths were first sighted in Mississauga in 1981 and are one of the most problematic defoliating insect pests in North America.

[Click to view the 2022 Aerial Spray Treatment areas]

The pesticide, Foray® 48B, contains a naturally occurring bacterium known as Bacillus thuringiensis sub-species kurstaki (Btk), which targets the larvae of specific moths or caterpillars. Btk is approved for use in Canada, and does not affect adult moths or caterpillars, other insects, honeybees, fish, birds or mammals. It is one of the few insecticides registered for use on organically grown fruits and vegetables, and the United States Environmental Protection Agency categorizes its risk to non-target organisms as minimal to non-existent. Peel Public Health does not expect any health impacts from the use of Foray® 48B during the City’s aerial spray.

The larvae ingest the Btk, which is designed to stick to leaves, and die when the bacteria produces a toxin that destroys their gut lining. The spraying is timed to coincide with a specific larval stage, to ensure the greatest success.

The spray will be applied twice, seven to 10 days apart, between 5 and 7:30 a.m., when wind and traffic are generally light. The university will take precautions, such as closing windows and sealing external vents, to ensure the pesticide stays outside.

Peel Public Health recommends that students/ faculty members stay indoors during the spray and for 30 minutes following the spray to allow the droplets to settle.

Before the spray, students/faculty should:

  • close all windows
  • turn off fans or air conditioners, or select the recirculate setting
  • bring in laundry
  • cover all vegetable and herb gardens
  • keep pets indoors
  • cover lawn furniture, bicycles and automobiles

After the spray, residents should:

  • wash/rinse lawn furniture and automobiles with water
  • Practice good personal and food hygiene (e.g. hand washing after outdoor activities, especially after gardening; leave outdoor shoes at the door; washing all fruits and vegetables before eating or cooking)
  • Wash pets’ paws before entering the home

For more information about the City’s LDD moth control program, visit www.mississauga.ca/2022spray or call 311 (905-615-4311 if outside City of Mississauga limits). Students or faculty members with any concerns or questions about health and the use of Btk can also call Peel Public Health at 905-799-7700.