Protecting Your Boxwoods: Gardenzilla’s Boxwood Pest Programs & Emergency Treatments

Boxwoods are the backbone of so many Toronto-area gardens. Their tidy, evergreen structure anchors formal hedges, frames front walkways, and holds a garden together through every season. But that same boxwood you’ve shaped and grown for years is now under pressure from several pests at once — and one of them, the box tree moth, can strip a healthy shrub bare in a matter of days.

At Gardenzilla, we’ve built a set of boxwood programs designed specifically for the threats facing GTA boxwoods, with proper timing built in and a competitive season-long option that we don’t think anyone else in Toronto is matching. Here’s what’s attacking your boxwoods, how we treat it, and what to do if you’re already seeing damage.

The four pests threatening GTA boxwoods

Box tree moth — the urgent one. Box tree moth was first detected in North America right here in Toronto, in 2018, and the GTA remains the epicentre of the infestation. The caterpillars are voracious: left unmanaged, larvae can defoliate an entire shrub, and once the leaves are gone they’ll chew on the bark and stems, which can kill the plant outright. They feed in multiple generations across the season — roughly mid-May into June, again mid-summer, and into early fall — which is exactly why a single spray isn’t enough to protect a boxwood through the year. If you see webbing, skeletonized leaves, or green-and-black caterpillars, this is the pest to act on immediately.

Boxwood psyllid. This sap-feeding insect causes the cupped, spoon-shaped leaves you’ll often notice on new spring growth. It rarely kills a healthy boxwood but disfigures the foliage and weakens the plant over time.

Boxwood spider mite. Mites cause fine stippling and a dull, bronzed look to the leaves, and they thrive in the warmer stretches of the season. Heavy populations leave foliage looking tired and discoloured.

Boxwood leafminer. The larvae feed inside the leaf itself, creating blister-like blotches and premature leaf drop. It’s one of the most common boxwood pests and, like the others, is best handled with well-timed treatment rather than a reaction after the damage shows.

Our boxwood program: the right treatment at the right time

The thing about boxwood pests is that timing is everything. The same spray that works in early May does nothing against a pest that emerges in late May, and a one-and-done treatment leaves your shrubs exposed for the rest of the season. Our program is built around the calendar these pests actually follow:

• Early May — horticultural oil targeting boxwood psyllid and spider mite, applied annually as the season gets going.
• Late May — horticultural oil targeting leafminer, timed to when the adults are active.
• BTK program — biweekly applications, 10 in total, starting in May for full-season box tree moth coverage.

BTK is a biological insecticide (Bacillus thuringiensis) that targets caterpillars specifically — it’s the same active ingredient the City of Toronto has used to manage moth larvae, and it’s safe around people and pets. Because box tree moth feeds in waves throughout the season, biweekly coverage is what actually keeps a shrub protected from spring through fall, rather than knocking back one generation and hoping for the best.

What sets Gardenzilla apart

Most companies will spray your boxwood once and move on. We built our programs to match how these pests actually behave, and to make protection easy to maintain year after year:

• Recurring applications, automatically timed. Our boxwood treatments are easy to add and recur at the correct point in the season, every year, so you’re never scrambling to book before a pest window closes.
• The only full-season biweekly BTK program in Toronto. As far as we know, no one else in the city offers 10 biweekly applications across the full box tree moth season. This is the level of coverage these shrubs actually need.
• A genuinely competitive price. Full-season biweekly BTK coverage is typically $485 for the season — a strong value for ten properly timed treatments, especially measured against the cost of replacing mature boxwoods.

Already seeing damage? Emergency treatments

If you’re noticing webbing, caterpillars, or rapidly disappearing foliage, you may already have an active box tree moth infestation — and waiting is not an option once they’re feeding. We offer two ways to respond fast:

• Emergency BTK treatment with a follow-up application one week later, to knock down the active larvae and catch any that were missed in the first pass, or
• A pro-rated continuation on our biweekly BTK program, so your emergency treatment rolls straight into full-season protection for whatever remains of the year.

The right choice depends on how far along the infestation is and whether you want one-time relief or ongoing coverage — something we can assess quickly on site.

Book an assessment

Whether you want to get ahead of the season with an ongoing program or you’ve spotted damage and need treatment now, Gardenzilla can help. Request a boxwood assessment and we’ll evaluate your shrubs, identify what’s attacking them, and recommend the right program or emergency treatment for your garden.

Reach out to Gardenzilla at gardenzilla.ca to request your assessment, ongoing program, or emergency treatment.