If you grow boxwood hedges or decorative shrubs (Buxus species) on your property, you may have already heard whispers of trouble: the Box Tree Moth (Cydalima perspectalis) is a rapidly spreading invasive insect now making waves in southern Ontario.
Its larvae are voracious leaf-eaters, able to strip foliage and—even worse—attack bark when populations surge. Here’s what to do about it.
How to Spot the Damage
Early signs can be subtle. Look for skeletonized leaves, ragged edges, webbing among foliage, or patches of frass (droppings). In heavier infestations, whole sections of your shrub may go bare. The caterpillars initially feed within the leaf layer, and as they mature, may chew deeper or cause bark damage
Because the moth is now regulated in Canada, any sightings are taken seriously.
Where It’s Found (and Spreading)
Box Tree Moth first showed up in Ontario in 2018, when a citizen scientist posted a detection in Toronto. Since then, it has spread through parts of southern Ontario, from Windsor and Niagara to the GTA, with regulatory zones established for nursery trade. Since the moth can fly an estimated 5–10 km per year on its own (and much farther aided by wind or by movement of infested plants), nearby properties, gardens and planting areas are at continual risk.
What You Can Do to Fight Back
- Monitor regularly: Inspect boxwood shrubs from spring through fall for leaf damage, webbing, or caterpillars.
- Time treatments: Because larvae feed during specific windows, biological sprays such as Bacillus thuringiensis (Bt / Dipel) (approved for caterpillar pests) are most effective when applied during early larval stages, typically mid-May to mid-June, then again mid-July to August.
- Prune and dispose: Heavily infested branches or shrubs may need pruning or removal. Once removed, bag and dispose of plant material carefully. Do not compost or dump nearby.
- Avoid moving infested plants: The pest is regulated. Moving infected boxwoods or stock can spread the moth to new areas and violate provincial rules.
- Report your sightings: Submit suspect specimens or photos to CFIA, Invasive Species Centre, or local plant health authorities. Early detection helps containment.
Think Twice About Boxwood
Given the rapid spread and severity of damage, some gardeners in the GTA are choosing to phase out boxwoods, opting for alternate shrubs less vulnerable to this insect. If you want suggestions about alternative plantings, our team is here to help.
Need Help with Boxwoods Under Attack?
If your boxwood shrubs show signs of damage, or if you just want peace of mind, our certified arborists and pest experts are ready to assist. Lawrence Park Complete Garden Care offers inspections, treatment planning, and regular monitoring so you don’t lose these shrubs you’ve worked so hard to cultivate.
