Domakihub How to Get Rid of Box Tree Caterpillar for Good
Spot the signs early, act fast, and protect your boxwood hedges and topiary.
Reviewed by Domakihub home & decor pros · 2026-06-23 · 5 min read
Box tree caterpillars (Cydalima perspectalis) have spread rapidly across Europe and are now a serious threat to boxwood hedges and topiary in Greek gardens, rental courtyards, and hotel grounds. Left unchecked, a single generation can strip an entire plant bare within days, leaving behind a distinctive tangle of white webbing and hollow brown shells where leaves used to be. The video above shows the infestation in action and the treatments that work; this article walks you through the exact steps to apply them yourself.
Why Box Tree Caterpillars Are So Destructive
The box tree moth (Cydalima perspectalis) is an invasive species originally from East Asia. It lays eggs on boxwood leaves, and the hatching caterpillars feed from the inside of the plant outward, which means damage is often severe before it is even visible from the outside.
In Greece's warm climate, the moth can complete two to three generations per year — spring, summer, and early autumn — meaning a hedge that looks healthy in April can be skeletal by July if monitoring is neglected. Hotels and holiday rentals with ornamental box parterres or clipped topiary are particularly exposed.
How to Identify an Infestation
Look for fine white webbing tangled between branches, small pale-green caterpillars with black heads and a yellow-green stripe along their sides, and patches of foliage that have turned brown or translucent. Frass (dark green droppings) visible at the base of the plant or caught in the web is another reliable sign.
Check plants at least monthly between March and October. Part the foliage to inspect the inner branches, as the caterpillars hide deep inside the canopy and the earliest feeding damage is internal. Catching an infestation at the first or second instar (larval stage) dramatically reduces the effort needed to treat it.
5 Steps to Get Rid of Box Tree Caterpillars
- 1
Remove webbing and visible caterpillars by hand
Put on gloves and use your fingers or a stiff brush to pull out all visible webbing, caterpillars, and pupae. Work from the outside in, then part the branches to reach the interior. Drop everything into a sealed plastic bag and dispose of it in general waste — not compost, as pupae can survive. This physical removal immediately cuts the population and allows any spray treatment that follows to penetrate the canopy.
- 2
Apply a biological insecticide (Bt-based spray)
Bacillus thuringiensis subsp. kurstaki (Btk) products — sold under trade names such as Xen Tari or Dipel — are the most effective and environmentally safe treatment. Mix according to label directions, then spray thoroughly over and deep into the plant, coating both sides of the leaves. The caterpillars stop feeding within hours of ingesting the bacteria and die within two to four days. Btk is harmless to bees, birds, and mammals, making it suitable for gardens near pollinators.
- 3
Re-spray after 10 to 14 days
A single spray application rarely eliminates an entire generation because newly hatched larvae emerge from eggs laid before or after treatment. Apply a second round of Btk 10 to 14 days after the first to catch any caterpillars that hatched in the interim. For severe infestations or late-season outbreaks when caterpillars are already large, you may need a third application.
- 4
Set pheromone traps to monitor adult moths
Hang one or two pheromone traps (such as Pherokart or equivalent) near your boxwood from April onwards. The lure attracts male moths, preventing mating and alerting you the moment the moth is active in your area. Check traps weekly; a sudden spike in catch numbers tells you to inspect plants immediately and time a spray application before the next generation of caterpillars hatches.
- 5
Feed and support the plant to aid recovery
Even after the caterpillars are gone, a heavily defoliated boxwood needs help to recover. Apply a balanced slow-release fertiliser in spring and again in early summer, and ensure consistent watering during dry periods. Trim away dead twigs to encourage new growth from the base, and avoid heavy pruning until the plant has put on a flush of new leaves. Most well-established box plants will recover fully within one to two growing seasons if the infestation is resolved.
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FAQ
- Can I use a regular pesticide instead of Btk?
- Chemical contact insecticides such as pyrethroid-based sprays will kill caterpillars on contact, but they also harm beneficial insects including bees and natural predators like wasps that prey on the moth. Btk is strongly preferred for garden and amenity use. If you do need a chemical option, apply it at dusk when bee activity is lowest and never when plants are in flower.
- Will my box hedge survive a full defoliation?
- In most cases, yes — established box plants are resilient and can regenerate from dormant buds even after complete defoliation, provided the woody stems and roots are still alive. Scratch a stem: if the tissue beneath the bark is green, the plant is alive. Remove dead wood, feed well, water regularly, and protect the plant from further caterpillar attack. Recovery typically takes one full growing season.
- How many times per year do I need to treat?
- In Greece's climate, plan for two to three treatment windows per year: late March to April (overwintered larvae resuming activity), June to July (second generation), and late August to September (third generation). Pheromone traps take the guesswork out of timing — spray within a week of a significant moth catch, before eggs have hatched into feeding caterpillars.