Top FAQs

It is recommended that residents avoid exposure to LDD caterpillars. Children should be discouraged from playing with any LDD caterpillars. The spiny hairs on the caterpillars can cause welts or a patchy rash that can persist for four to five days. Residents experiencing symptoms are advised to contact a heath care professional for advice.

Aerial spraying involves spraying an area of tree canopy a compound containing a substance called Bacillus thuringiensis subspecies kurstaki (Btk), (Btk) from the air using a double engine helicopter. When employed, this work is completed by a contractor working for the city.

The City’s spray zones encompass the areas predicted to have the greatest risk to tree health from defoliation cased by LDD in 2022. They were derived from detailed LDD monitoring data collected by the city’s consultants in the fall of 2021. There will still be LDD present elsewhere in the city. Outside of the spray areas the city will also be undertaking other measures such as egg mass scraping and ground-based treatments to help reduce impacts on the urban forest and to help residents preserve and protect tree health. Materials and information will also be provided for residents in affected areas to help combat LDD on their properties. The City’s website mississauga.ca/LDD contains tools and resources for landowners on what they can do on their own properties to combat LDD including pest control techniques and a reporting form to submit observations of LDD.

The aerial spray treatment is one component of the City’s Integrated Pest Management program to address LDD. Where spraying is not advantageous, ground based treatments including egg mass scraping, tree injections and/or ground sprays may be used to control localized LDD infestations on City trees.

Btk is an effective pesticide that has been shown to successfully manage LDD populations. It has been extensively studied by Health Canada and the US Environmental Protection Agency (EPA). Research shows that Btk poses minimal risk to human health when used as directed.