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Garden & Horticultural SocietyBeautifying Richmond Hill since 1914

Boxwood Caterpillar (aka The Box Tree Moth)

June 28, 2023 9:00 AM | Anonymous member (Administrator)

I noticed significant damage and caterpillars on my boxwoods in early June, which led me to do some research. Not only do we need to be aware of the boxwood blight in this province, but now also the Boxwood caterpillar or, officially, the box tree moth. For a while it seemed to be limited to as far as Etobicoke, but now is spreading through York Region. I mentioned it to several neighbours who also have boxwood on their property, and indeed, it seems to be moving through the neighbourhood. Hort members, be aware!

Here is a photo I took of the caterpillar in my Box Wood.

I reported my sightings to Landscape Ontario so that others are aware of this current issue. I found some very useful information on their site as well. Their link is in the references below.

Key information is copied below with some of my comments: 

  • Box Tree Moth can be a significant pest if left unmanaged. Spread the word about box tree moth to your local horticultural networking group and encourage others to monitor boxwood for this pest.
  • Box tree moth can be easily controlled if it is sprayed at the right time. A product called BTK is recommended for treatment.  It is the same ingredient that was used for the spraying of the Gypsy Moth.  I have found this product at Canadian Tire. 
  • There are THREE active stages for this moth throughout the season:  Continue to monitor boxwood plants for signs of active larval stages, especially during the periods of May 30 to June 15,  July 15 to Aug. 10,  and Sept. 1 to 15.

The Landscape Ontario site is an excellent and informative source of information  in my opinion, a MUST READ for anyone who suspects infection.  It is further helpful as it also distinguishes between other insects/infections that may be the culprit in our boxwoods. 

- Landscape Ontario website for the Box Tree Moth:

Article & Photo by Monica Ahrens, a member of the Richmond Hill Garden & Horticultural Society

Member of the Ontario Horticultural Association

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