How do I tell box blight from box tree caterpillar?

Look for webbing. Caterpillar damage comes with webbing over the foliage, green-and-black larvae inside it, frass and leaves stripped to bare twigs. Blight shows dark streaks or lesions on the stems, leaves turning straw-brown and dropping, and in damp weather a fine white spore bloom on the leaf underside.

Will a box hedge with blight recover?

Sometimes, with cutting out, litter clearance, better air movement and treatment — but it is a long job and reinfection is common in humid conditions. On a badly affected hedge, replacing with a less susceptible species is a reasonable choice rather than a failure.

Can I compost clippings from an affected hedge?

Better not to. Bag and dispose of affected clippings and fallen leaves rather than composting them or leaving them under the hedge, because both spores and caterpillar stages can carry over.

Is brown box always a pest or disease?

No. Cold winds, hard frost, waterlogging and drought all brown box foliage without any pest or pathogen involved. That is exactly why identification comes before treatment.

Low risk

Updated 30 August 2026

Box Hedge Turning Brown And Bare

Box hedging or topiary has gone brown and lost its leaves in patches, and bare woody stems are showing through.

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Garden maintenance work, illustrative image

What's happening?

Brown box is nearly always one of two problems, and they are distinguished by looking closely rather than from a distance. Box blight is a fungal disease: it produces dark streaks or lesions on the stems, straw-coloured or brown leaves that fall, and in damp weather a fine white bloom of spores on the underside of affected leaves, spreading fastest in humid, still, congested growth. Box tree caterpillar is an insect: the larvae feed inside webbing spun over the foliage, strip leaves down to bare twigs and leave visible green-and-black caterpillars, webbing and frass. The reason to get the identification right is that they are managed in completely different ways — hygiene, air movement and fungicide for one, and monitoring, physical removal and biological control for the other. A hedge can carry both at once.

What usually causes it?

Box blight infection spreading in humid, still conditions and dense congested growth
Box tree caterpillar larvae feeding inside webbing and stripping the foliage
Overhead watering or trimmings left in the hedge, keeping the foliage wet and spreading spores
Infected new plants or tools bringing blight into a previously clean hedge
Clipping in warm humid weather, creating fresh cuts for infection
Winter cold, wind, waterlogging or drought stress in a dry, root-competitive spot, causing browning that is neither pest nor disease
Thick clipped shells with dead congested growth inside and no air movement

Is it dangerous?

No. It is a plant health problem. What it does carry is a spread risk to other box in the garden and in neighbouring gardens, which is why clippings and fallen leaves from an affected hedge should be bagged and disposed of rather than composted or left on the ground, and why tools should be cleaned between plants.

Can I fix it myself?

Get on your knees and look. Webbing with green-and-black caterpillars inside means box tree caterpillar; dark streaks on the stems with leaves dropping and a white bloom on the leaf underside in damp weather means blight. Cut out and bag affected material, clear all fallen leaves from beneath the hedge, and clean tools between plants. Improve air movement by thinning the growth, water at the base rather than over the top, and avoid clipping in warm humid spells. Caterpillars can be picked off and webbing removed by hand on a small hedge. Whether to keep going with box or replace it with a different species is a legitimate decision, not a defeat.

When should you call a gardener?

Call a gardener if you are not certain which problem you have, if it is spreading through the hedge despite what you have done, or if the hedge is large enough that hand-picking and cutting out is impractical. A gardener will also advise honestly on the point at which replacement beats treatment, and on alternative species that give a similar look without the same vulnerability — which is often the sensible answer for a long hedge that has had blight for several seasons.

What will the gardener actually do?

Inspect closely to identify blight, caterpillar, or both, and rule out cold, drought and waterlogging damage
Cut out and bag affected growth, and clear fallen leaf litter from beneath the hedge
Thin congested growth to increase air movement through the plant and speed drying
Apply appropriate treatment for the confirmed problem, timed to the disease conditions or the caterpillar's life cycle
Set up monitoring so caterpillar generations are caught early rather than after defoliation, and adjust watering, feeding and clipping timing to reduce the conditions that favour infection
Advise on replanting with a less susceptible species where the hedge is beyond recovery

Frequently asked questions

We’re happy to answer all your questions.

Sources & References

Hedge Overgrown And Out Of ShapeCaution Toadstools And Fungus In The LawnCaution Garden Completely OvergrownCaution

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