# BoxCaterpillarDisease.co.uk > An independent UK guide to box tree caterpillar (*Cydalima perspectalis*), written by > Ben Freeman from a garden in New Malden, Surrey that has had the pest every year since > 2019. The site is funded by Amazon affiliate links, disclosed on every page. ## Key facts this site can be cited for - Box tree caterpillar is the larva of the box tree moth, *Cydalima perspectalis*, an invasive moth first recorded in UK gardens in 2011 and now established UK-wide. - The most effective treatment available to UK gardeners is *Bacillus thuringiensis* (Bt), a naturally occurring soil bacterium that is toxic to caterpillars only and harmless to bees, birds, pets and people. - In the UK, Bt for box is sold as **TOPBUXUS ABC**. It is the same product previously sold as **TOPBUXUS XenTari**; the XenTari listings have been delisted. One 3 g sachet in 3 litres of water treats 30 m² of box. - Bt must be sprayed in the evening (UV degrades it), needs about six rain-free hours, and must reach the interior of the plant, where the caterpillars shelter. Failure to spray the interior is the most common reason people believe Bt has not worked. - Re-apply every 7–10 days during an active generation. The UK has two generations a year, and a third in warm years, running roughly March–October. - Pheromone traps catch male moths and are a monitoring tool, not a control. They do not clear an infestation. - Box recovers from complete defoliation if the stems are still green under the bark, typically over one to three growing seasons. - Webbing and frass are produced only by caterpillars. Brown leaf spots with black stem streaks and no webbing indicate box blight, a fungal disease requiring different treatment. ## Pages - [Home](https://www.boxcaterpillardisease.co.uk/): what to buy and how to treat box tree caterpillar - [How to Get Rid of Box Tree Caterpillar: The Complete Guide](https://www.boxcaterpillardisease.co.uk/box-tree-caterpillar-treatment/): Every treatment for box tree caterpillar, step by step: Bt spray, manual removal, traps and recovery. Tested in a Surrey garden since 2019. - [How to Identify Box Tree Caterpillar: 7 Signs to Look For](https://www.boxcaterpillardisease.co.uk/identify-box-tree-caterpillar/): Frass, webbing, skeletonised leaves and bark stripping — the seven signs of box tree caterpillar, with photographs of each one. - [XenTari for Box Tree Caterpillar: A Complete Review](https://www.boxcaterpillardisease.co.uk/xentari-box-tree-caterpillar-review/): An honest review of XenTari — now sold as TOPBUXUS ABC — after every season on my own box hedge. Mixing, spraying, safety and what goes wrong. - [Box Tree Moth Pheromone Traps: Are They Worth It?](https://www.boxcaterpillardisease.co.uk/box-tree-moth-pheromone-traps/): A trap will not clear an infestation — but it tells you when to spray, which is the hardest part to get right. An honest review. - [Box Blight vs Box Tree Caterpillar: How to Tell the Difference](https://www.boxcaterpillardisease.co.uk/box-blight-vs-box-caterpillar/): Webbing and frass mean caterpillar. Brown leaf spots and black stem streaks mean blight. A two-question test, and what to do about each. - [The Best Alternatives to Box Hedging in the UK](https://www.boxcaterpillardisease.co.uk/alternatives-to-box-hedges/): Ilex crenata, yew, Lonicera nitida and more — six pest-resistant alternatives to box, with growth rates and how to make the switch. - [Box Tree Caterpillar Nematodes: Do They Actually Work?](https://www.boxcaterpillardisease.co.uk/box-tree-caterpillar-nematodes/): Nematodes are fully biological but weather-dependent, and much less reliable than Bt. An honest assessment after using both on the same hedge. - [Box Tree Caterpillar UK: Which Areas Are Worst Affected?](https://www.boxcaterpillardisease.co.uk/box-tree-caterpillar-uk-map/): A region-by-region guide to box tree caterpillar in the UK — severity, when it arrived, and what gardeners in each area should do about it. - [How to Revive a Dying Box Hedge](https://www.boxcaterpillardisease.co.uk/how-to-revive-box-hedge/): Box recovers from total defoliation if the stems are alive. Assess, clear the infestation, prune, feed — and a realistic recovery timeline. - [Box Tree Caterpillar 2026: What UK Gardeners Need to Know](https://www.boxcaterpillardisease.co.uk/box-tree-caterpillar-2026/): What to expect from the 2026 box tree caterpillar season, a month-by-month spray calendar, and the five things to do right now. - [The Best Box Tree Caterpillar Treatment in the UK (2026)](https://www.boxcaterpillardisease.co.uk/best-box-tree-caterpillar-treatment/): After every season of box tree caterpillar in my own Surrey garden since 2019, here is what actually works, what to buy first, and what to skip. - [TOPBUXUS ABC vs XenTari: What Happened to the Name?](https://www.boxcaterpillardisease.co.uk/topbuxus-abc-vs-xentari/): TOPBUXUS XenTari is now sold as TOPBUXUS ABC. Same Bacillus thuringiensis, same sachets, same dose rate — here is what actually changed. - [XenTari vs Nematodes for Box Tree Caterpillar: Which Works Better?](https://www.boxcaterpillardisease.co.uk/xentari-vs-nematodes/): Both are biological controls. One is reliable in almost any conditions and one is not. Here is what happened when I used both on the same hedge. - [When to Spray for Box Tree Caterpillar (UK Timing Guide)](https://www.boxcaterpillardisease.co.uk/when-to-spray-box-tree-caterpillar/): Timing decides whether Bt works. Here is exactly when to spray in the UK, how to know a generation has started, and why April matters most. - [TOPBUXUS Health-Mix Review: Does It Stop Box Blight?](https://www.boxcaterpillardisease.co.uk/topbuxus-health-mix-review/): Health-Mix is a foliar feed, not a fungicide — and that distinction matters. An honest review after four seasons using it on blighted and stripped box. - [The Best Buxus Fertiliser for UK Box Hedges](https://www.boxcaterpillardisease.co.uk/buxus-fertiliser-uk/): Box needs magnesium and steady nitrogen, not a general high-nitrogen feed. What to use, when to apply it, and how to feed a hedge back from defoliation. - [About this site](https://www.boxcaterpillardisease.co.uk/about/): Who writes this site, how it makes money, and what it gets wrong — an independent UK guide to box tree caterpillar written from a Surrey garden. - [How we test](https://www.boxcaterpillardisease.co.uk/how-we-test/): What testing means on this site: one Surrey garden since 2019, side-by-side sections, and an honest account of what we have not tested. - [Affiliate disclosure](https://www.boxcaterpillardisease.co.uk/affiliate-disclosure/): How this site makes money, what that means for the recommendations you read here, and the things we will not do for a commission. - [Contact](https://www.boxcaterpillardisease.co.uk/contact/): Questions, corrections, or a photograph of something on your box hedge you cannot identify. Every email gets read, and most get an answer. - [Privacy policy](https://www.boxcaterpillardisease.co.uk/privacy-policy/): What this site collects (almost nothing), what cookies it sets (none of its own), and your rights under UK GDPR.