Green caterpillars on boxwood


I live in Toronto and for the second year I find green caterpillars on my boxwood. Last June I picked up by hand at least 200 of them. Yesterday I noticed droppings underneath the boxwood shrub which was nearly denuded last year and which had just a few new leaves that now are nearly all eaten. Again I have picked up about a hundred caterpillars. Is there anything else I can do to kill them this year and prevent them from reappearing next spring?
Another related question: Some of my peonies had some of their leaves partly eaten up and now that they have unfurled look disfigured. This morning I found one of the same caterpillars (the smaller one on the photograph) that attacked the Boxwood on one of the peony plants. It looks like these caterpillars eat peonies as well.
I hope you can give me some advice, I have had the boxwood and the peonies for many years and I hope not to lose them.
Thank you very much
P.S. I am having trouble sending you the photos of the offending caterpillars, the fully grown ones are an inch long, green with a black head and with pairs of black dots facing all along their back. They also have white thorn like hairs along the body


While without a photo it is difficult to accurately determine which pest is damaging your boxwoods, your description is consistent with the larvae of the Box Tree moth (Cydalima perspectalis). Your initial approach of removing the larvae is appropriate. That you were alert to identifying the presence of young larvae (caterpillars) this year is also good. Removing the pest in a timely manner will help the health of your boxwoods. Please click on the following link – Box tree moth: A new plant pest in Etobicoke. This article describes the larval and adult stages of this insect, with photos, and will help you with accurate identification. Under the headings: “Management” and “What you can do”, you will find measures to manage this pest. Consistency is important and the article sets out dates and steps to take in caring for your boxwoods.

Box Tree Moths are relatively new to our area (since 2018) and research into prevention, control and treatment continues. The presence of the larvae on peonies will likely be of interest to the horticultural researchers. It is recommended that you take photos of these larvae on both plants so that this can accompany any report you may complete. Please report to at least one of the following organizations:

For more information, please see the webinar: Detecting, Identifying and Managing Box Tree Moth

Wishing you all success in managing this pest.