What is the name of the bio-pesticide that will be used?

    The aerial spray program will be using a biological insecticide called Foray 48B Biological Insecticide Aqueous Suspension, its active ingredient is Bacillus thuringiensis v.kurstaki. Registration No. 24977 under the Pest Control Products Act (Canada) for the management of European Gypsy Moth (EGM).

    What is Bacillus thuringiensis v.kurstaki or Btk?

    Bacillus thuringiensis v.kurstaki, or commonly known as Btk, is a naturally occurring soil bacteria that is present in our environment. It is not a chemical and is certified for organic use in Canada. Bacteria are present everywhere in our natural environment: in soil, food and even on our skin. Bacillus thuringiensis (Bt) is a bacterium found naturally in the soil.

    Why is Bacillus thuringiensis kurstaki (Btk) being sprayed?

    Data collected on EGM over the past two years has shown that the EGM population is healthy, growing and spreading. This is not just unique to London. Across southern Ontario last year there were record breaking population levels of EGM. In the five (5) locations that are to be sprayed, trees have experienced severe defoliation, in one case up to 100%. These locations have also been identified as having a large population of oak tree stands. Oak trees are one of our most important tree species in the Carolinian Forest. They are some of our largest and oldest trees known as keystone species. Keystone tree species over their life time support hundreds of different types of animals, insects, birds and reptiles.    

    Aerial spraying can target the caterpillars in tall tree canopies where other techniques cannot do so as effectively and easily.


    How effective is spraying Bacillus thuringiensis kurstaki (Btk)?

    Spraying Btk is not a "silver bullet" solution to the EGM outbreak. It will not eradicate EGM but it will reduce populations to more manageable levels to protect tree canopies. Also, it takes time to have effect and will not destroy caterpillars immediately. It can 2-4 days depending on caterpillar size. Larger caterpillars may even survive the spray event. Aerial spraying Btk is only one “tool” in the EGM toolbox and why other management techniques such as burlap banding should also be used.

    Ultimately it will be natural causes such as the buildup of predators (virus, fungus, parasitic wasp) that will cause the outbreak to collapse.


    How will Bacillus thuringiensis kurstaki (Btk) be sprayed?

    The product is applied directly to tree foliage by a twin-engine helicopter equipped with an ultra- low-volume spray system. The aircraft flies about 15 to 30 metres above the tree canopies. Residents can expect high audible levels as the helicopter completes its once over path.

    City of Toronto Aerial Spray Program


    When will Bacillus thuringiensis kurstaki (Btk) be applied?

    This web page will be updated to reflect a confirmed date including any weather delays.

    Btk is timed to be applied when there are as many as possible caterpillars feeding in the tree canopies. The factors that affect this are leaf area and caterpillar stage. Leaves should be large enough to provide area for the spray to land on and for the caterpillars to eat. The one aerial application of Btk will be timed when 90% of the EGM eggs have hatched, climbed into the tree canopies, and are feeding. This means that some very early and very late emerging caterpillars may not be affected. This year it is projected to be in mid-May during the week 17-22. Weather such as wind and rain impacts when Btk can be applied and there may be delays and the spray rescheduled.

    Is Bacillus thuringiensis kurstaki (Btk) safe to people?

    Civic Administration has looked at this very carefully and consulted with the Middlesex-London Heath Unit. According to Health Canada, Btk poses little threat to human health either through handling products directly or through indirect exposure such as aerial spraying. The public are unlikely to experience any symptoms if inadvertently exposed to Btk spray, and no special precautions are necessary or required. Btk is approved by the Pest Management Regulatory Agency (PMRA) of Health Canada and has been in use for over 30 years in urban areas. Btk has been used safely and effectively managing EGM in other aerial spray municipal programs such as Toronto, Oakville, Sarina, and Hamilton.

    Btk does not affect other insects such as honeybees, or animals like fish, birds, or mammals. Btk only works in the alkaline stomach of the caterpillar stage of moths and butterflies

    Is Bacillus thuringiensis kurstaki (Btk) safe to animals or other insects?

    Btk does not affect other insects such as honeybees, or animals like fish, birds, or mammals. Btk only works in the alkaline stomach of the caterpillar stage of moths and butterflies. Btk produces crystals that break down the caterpillar’s stomach causing it to stop feeding. It will affect caterpillars that are feeding at the same time as the EGM caterpillar such as the tent caterpillars. Civic Administration researched what has done to mitigate the risk to the Monarch Butterfly caterpillar stage. As a result, only a single application of Btk will be applied so that the overlap in lifecycles is unlikely.  

    What personal precautions can be taken in preparation for aerial spraying?

    It is very unlikely that residents will experience any symptoms. However, residents who have concerns in the same way they would avoid pollen or other airborne materials during days when air quality advisories are issued. Exposure can be reduced by staying indoors with windows and doors shut during the spray period.

     Some other actions to consider for residents living in treatment areas include:

    • Bring inside pets before spraying begins.
    • Cover outdoor items such as lawn furniture, BBQs, play equipment and/or rinse them off with water after spraying is completed.
    • Limit opening and closing windows and doors during the spraying.
    • Shutting off the heating/cooling vents or selecting the recirculate setting.
    • Remain indoors for 30 minutes after spraying to allow for the droplets to deposit onto the tree leaves
    • Wash fruits and vegetables from your garden before eating or cooking.

    Contact your family physician if you are concerned that a personal medical condition may be aggravated by the spraying.

    What should I do if I experience an adverse reaction?

    If you experience an adverse reaction or any worsening medical condition, speak to your physician or, in an emergency, call 9-1-1.

    Should I contact the Middlesex-London Health Unit (MLHU) to report medical concerns or a pesticide incident?

    No. The Middlesex-London Health Unit does not regulate the use pesticides. Pesticides are regulated through Health Canada’s Pest Management Regulatory Agency (PMRA).  

    Medical Concern:

    If you experience an adverse reaction or worsening medical condition, speak to your physician or, in an emergency, call 9-1-1.

     Pesticide Incident:

    Report the incident directly to Health Canada’s Pest Management Regulatory Agency via their Public Engagement Portal Voluntary Incident Reporting Form. 

     The form included in the portal allows you to report on the following:

    • Human Health Incident
    • Domestic Animal Incident
    • Environmental Incident