I just today realized that the deterioration of my 10 boxwoods shrubs this spring is because of box tree caterpillar.
At this point they are about 30-50% decimated.
I see that there is an organic treatment called BTK available at Canadian Tire, but I am wondering if there is any point to try to save the shrubs at this point.
Should I just toss them out and make the decision to play t something else.
I am concerned about eggs in the soil around the shrubs.
Will these caterpillar eat any shrubs nearby? I have emerald cedars, deutzia, hydrangea, Korean lilac.
Thank you very much for any help with my 2 questions.
Sorry you’re dealing with this issue! While without a photo it is difficult to accurately determine which pest is damaging your boxwoods, here is some advice for managing the Box Tree moth (Cydalima perspectalis).
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.
With regard to a treatment for Box Tree Moth Landscape Ontario recommends the following “Box tree moth larvae can be effectively managed with a safe biological insecticide (Dipel 2X DF PCP#26508), a product already registered for use in Canada. In fact, this is the same biological insecticide that is applied by air over the City of Toronto to combat Gypsy moth larvae in the spring. Dipel 2X DF contains a naturally occurring bacterium, Bacillus thuringiensis (B.t.), that when sprayed on the foliage, is consumed by the larvae as they feed on the leaves. Within an hour of ingesting the B.t. residue, the larvae stop feeding and then die within two-three days. Foliage needs to be retreated at least every 10 days to keep an effective layer of B.t. on the leaves during periods of larval activity. We found that one application per larval generation was usually enough to kill actively feeding larvae.” Bacillus thuringiniensis (B.t.) is available at your local garden center. Make sure to read directions on the label before applying.
I understand your concern with the pest migrating to your other plants. Box Tree Moths are relatively new to our area (since 2018) and research into prevention, control and treatment continues. The Box Tree moth primarily uses Boxwoods (Buxus) plants as hosts, but a few other plants have been recorded as hosts in Asia as outlined in this fact sheet: https://inspection.canada.ca/plant-health/invasive-species/insects/box-tree-moth/fact-sheet/eng/1552914498593/1552914498889
For additional information on this pest:
Landscape Ontario box tree moth resource page: https://landscapeontario.com/tag/box%20tree%20moth
Ontario nursery crops blog (also for landscape plants) by Jen Llewellyn; search box tree moth: https://onnurserycrops.com/
For more information, please see the webinar: Detecting, Identifying and Managing Box Tree Moth
Wishing you all success in managing this pest.