If your box hedge is turning brown and covered in webbing, you almost certainly have box hedge caterpillars - the larvae of the box tree moth. They can strip a healthy hedge in a couple of weeks, and because there are at least two generations a year they keep coming back until the infestation is dealt with properly. JG Pest Control treats box tree moth caterpillars across the UK, with same-day visits often available. We are open every day except Christmas Day, early until late.
Box is the target
The caterpillars feed almost entirely on box (Buxus), so hedging, topiary and parterres take the damage.
At least two generations
There are at least two generations a year, and most of the damage happens between March and October.
They spend winter in the hedge
Small caterpillars overwinter inside box leaves webbed together in autumn, ready to feed again in spring.
Early spring is the time to act
Treating the first caterpillars of the year saves the most foliage, with checks through the summer for the next generation.
What are box hedge caterpillars?
Box hedge caterpillar, box tree caterpillar, box moth caterpillar and buxus caterpillar are all names for the same insect: the larva of the box tree moth (Cydalima perspectalis), which many people call the box hedge moth or simply the box moth. The moth arrived in the UK from East Asia in the 2000s and is now widespread, with London and the South East hit hardest, and it has since spread across much of England and into Wales, Scotland and Ireland.
The caterpillars feed almost exclusively on box (Buxus) - the slow-growing evergreen used for hedging, topiary and parterres. A heavy infestation can defoliate plants that took decades to grow, which is why early treatment matters so much.
How to identify box tree caterpillars
- The caterpillars. Greenish-yellow with thick black and thin white stripes, a shiny black head, and fine bristles. They grow to around 4cm.
- Webbing. Fine, pale webbing spun over and inside the hedge is usually the first thing people notice - the caterpillars feed under its protection.
- Patchy dieback. Leaves are eaten from the inside of the plant outwards, so damage is often well advanced before the outside of the hedge looks wrong.
- Pale pellets. Greenish-yellow frass (droppings) collects on and under the plant.
- The moths. Usually white wings with a brown border (some are all brown), around 4cm across, flying from late spring to autumn.
Box tree caterpillar or box blight?
Brown, bare patches in box can have several causes, including drought and winter scorch, but the two most common are box tree caterpillar and box blight, and they need different treatment. Box blight is a fungal disease; box tree caterpillar is an insect pest. Look closely before you do anything:
Signs of box tree caterpillar
Fine webbing over and inside the plant, green-and-black caterpillars, chewed leaves with curved bites taken out, and pale droppings under the hedge.
Signs of box blight
Leaves turn brown and fall, black streaks appear on young stems, and white fungal growth can show under the leaves in wet weather. There is no webbing and no caterpillars.
Box blight spreads in warm, humid weather and is a plant health problem, not a pest one. If you are not sure which you have, send us a photo and we will tell you whether it looks like caterpillar damage.
The box tree caterpillar year
- Winter. Small caterpillars shelter inside box leaves they webbed together in late autumn.
- Early spring. They wake and start feeding again, usually from March, from the inside of the plant outwards.
- Late spring to early summer. The overwintering caterpillars finish feeding, pupate in the hedge and emerge as moths, often by June. These moths lay eggs, and a new generation of caterpillars hatches and feeds into the summer.
- Late July to August. A further flight of moths emerges and lays eggs, so fresh caterpillars feed through late summer.
- Autumn. By late September and October most of the caterpillars are small again, and they spin in for the winter.
What to check through the year
- From early spring, part the outside of the hedge and look inside for webbing, droppings and small caterpillars. Damage starts in the middle, so the outside can look fine for a while.
- Pheromone traps catch male moths and show you when they are flying, which tells you when the next generation of caterpillars is due. They are a monitoring tool and will not control an infestation on their own.
- After a treatment, keep checking through the summer, because moths from neighbouring gardens can lay a fresh generation.
Why they are so destructive
Box tree moths produce at least two generations a year in the UK, and most of the damage happens between March and October. With more than one generation feeding through the year, a hedge that looked slightly thin in May can be brown and bare by August. The caterpillars also strip bark from stems, which can kill the plant even where some leaves survive. Because the moth has few natural predators here, infestations rarely burn out on their own.
Professional box hedge caterpillar treatment
Our technicians treat the caterpillars directly, using professional products applied into the webbing and inner foliage where they hide - the area garden sprays rarely reach. Treatment is timed to the life cycle, because eggs and pupae are far tougher than feeding caterpillars, and we advise on follow-up visits where a second generation is likely. Our technicians hold the RSPH (BPCA) Level 2 Award, trainees work alongside qualified colleagues, and our work is guaranteed.
If you have a wider caterpillar problem - including nests of other species around the garden - see our caterpillar pest control service.
Can a box hedge recover?
Often, yes. Box is surprisingly resilient: if the infestation is stopped before the bark is stripped, most hedges re-leaf over the following season. Feed and water the plant after treatment, trim out dead wood, and keep an eye out for fresh webbing from late spring onwards. Where plants are too far gone, we can advise on whether replanting or switching to a box alternative makes more sense.
Frequently asked questions
If you can see webbing, green-and-black striped caterpillars and patchy brown dieback, it is the box tree caterpillar - the larva of the box tree moth. It is by far the most common cause of sudden box hedge damage in the UK.
They are not dangerous to people or pets - the damage is to the plants. The main risk is losing mature box hedging and topiary, which is slow and expensive to replace.
Light pruning helps you find the caterpillars but rarely stops an infestation, because eggs and larvae are spread through the whole plant. Professional treatment targets the caterpillars inside the webbing where trimming and shop sprays miss them.
While caterpillars are actively feeding - typically from March to October. The earlier in an outbreak you treat, the more of the hedge you save. We are open every day except Christmas Day, so you will not wait long for a visit.
It can, because adult moths fly in from surrounding gardens. After treatment we advise monitoring from spring; catching the first generation early makes each following year easier.
Box tree caterpillar leaves webbing, caterpillars, chewed leaves and pale droppings. Box blight, a fungal disease, turns leaves brown so they fall, leaves black streaks on young stems and has no webbing. They need different treatment, so it is worth checking closely or sending us a photo.
They stay in the hedge. Small caterpillars overwinter inside box leaves they have webbed together in late autumn, then start feeding again in spring.
The overwintering caterpillars usually start feeding again from March. There are at least two generations a year, so fresh caterpillars can appear again in late summer.
No. They catch some male moths and show you when the moths are flying, which helps time treatment, but they will not clear an infestation on their own.