Garden Advice

Box Tree Caterpillars Invasion: How to Get Rid of Box Moth Caterpillars

Image source: Eileen Kumpf /

The box tree caterpillar is an insect native to eastern Asia. However, it’s an invasive species and can even be spotted around Europe. As a matter of fact, these green and black caterpillars are newcomers to the UK and arrived with imported Buxus plants. These box moth caterpillars were first spotted in the UK in 2008.

Box tree caterpillars are one of the UK’s most harmful insects. And although pretty to look at, these species of caterpillars are a huge threat to box trees and good-looking topiaries alike.

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So if you:

  • Are a proud owner of a garden full of box plants;
  • Have box trees, but they look faded and desiccated lately;
  • Have you seen box tree moths flying around your garden and you searching for box caterpillar treatment;
  • Are you concerned about the health of your box hedges;

Then you are in the right place so keep reading.

How can you tell if caterpillars are eating your box tree?

Webbing and caterpillars on box plants are likely to alert gardeners to box tree caterpillars. They are bright green, with black heads and have lines on their body. These insects mask themselves with a cover of webbing to hide from predators. The damage caused by box hedge caterpillars can often be mistaken for box blight. However, if you look close enough and notice eaten leaves coated with webs, you must act quickly.

What is the life cycle of a box tree caterpillar? The box tree caterpillar’s life cycle begins with larvae, so tiny they cannot be seen with the naked eye. Newly hatched, the Buxus caterpillars are greenish-yellow with black heads. In four weeks, they reach a length of 3-4 cm, shortly before becoming an adult box tree moth. In the UK, these black and green striped caterpillars can produce up to 3 generations of moths in just a year.

The worst part is that these ruthless bugs have an impressive way of concealing their presence. They disguise themselves amongst the foliage, wrapped in webbing. This method protects their babies and provides them with a safe environment. Their box-green colour also plays a major role in their camouflage game. By glueing themselves to the branches, they become almost invisible.

What does box tree caterpillar damage look like?

Webbing (like a spider web) and caterpillar green excrement at the base of the plant are the first signs of caterpillar damage. The young caterpillars eat only a small part of the plant, while the older ones cause most of the damage by completely defoliating the box tree.

Adult caterpillars can ruin the plant beyond recognition, leaving it with skeleton-like leaves in a short amount of time. Box tree caterpillar damage can be easily recognized by the spider mites left in their wake. Although the plant may look bare and dead, the box tree will grow green once again, thanks to its excellent healing ability.

However, it can be fatal for the box tree if the bark is attacked or if the plant has been eaten repeatedly. These occurrences will cause it to become dry and die eventually. These occurrences will cause it to become dry and die eventually.

All we know is that Buxus grows slowly, and replacing all the mature topiaries and hedges in our garden can be really expensive. Anyway, if you need some new hedges or other greenery replanted, you can always count on our professional garden planting services.

Remember that July and April are the months when these moths are the most active, so always be on the lookout for box moth webs and other clues like eaten leaves.

Can box trees recover from caterpillars?

Yes! Box plants are resilient species, and once an infestation has been resolved, they will actually sprout after eight weeks.

Do box tree caterpillars eat other plants?

No, box tree caterpillars rarely eat any other plant. Box tree caterpillars and moths mostly prefer Buxus, so the probability of them invading other plants is minimal. However, we should be careful with Japanese spurge, which is used and sold as a box tree replacement. Since it’s a part of the Buxaceae family, it’s very likely to be eaten by box tree caterpillars.

However, it has to be nearby an infected Buxus shrub to be affected by the caterpillars.

Dealing with overgrown hedges?

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Dealing with overgrown hedges?

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Why are box tree caterpillars expanding so quickly?

Box hedge caterpillars are one of the most invasive species in eastern Asia. However, with the help of predacious wasps, their population is limited and kept under control. Unfortunately, we don’t have such wasps in the UK, and our natural and native hedge protectors – the birds, are not interested in a box caterpillar lunch.

Due to the toxins in the box tree leaves, caterpillars taste terrible and are not a food source option for them. Without any box caterpillar-loving birds, it’s up to us to keep this pest under control. Unless we take things into our own hands, we can expect things to worsen.

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How to get rid of box tree caterpillars

Hand Picking

Hand-picking is probably the most time-consuming yet the most effective box tree caterpillar treatment. The caterpillars should be removed by hand whenever possible or pruned out of the stems that have been covered in the webbing and caterpillars and destroyed. If you are up for this method, be warned that there is a risk of an allergic reaction.

As they are not native to the UK, make sure to wear gloves and a protective breathing mask. The best way to remove box tree caterpillars is to pick them up thoroughly and rub the underneath of leaves to remove any eggs of theirs.

Using box tree pheromone traps

Another form of biological control for box tree caterpillars is using pheromone traps. They contain a specific pheromone that attracts the male moths and traps them. After that, the moths are sent to their watery grave. This reduces the number of male moths, which leads to fewer female eggs. Remember that this method is used only for monitoring. These traps can’t help you eliminate the caterpillars but will reduce them.

Organic insecticides

If caterpillars appear on a box tree, you can try to handle them with a natural pyrethrum spray. It’s an organic box tree caterpillar insecticide made from the chrysanthemum flower. The bad news is that this kills only the caterpillars that were in direct contact with the spray. The plant cannot absorb it as it can also kill other insects. You can also read our post on natural homemade pesticides and choose a spray from there.


Nematodes are tiny worms that kill the box tree caterpillars by entering their bodies through natural openings and producing bacteria which disrupt their digestive system and prevent them from feeding on plants. The nematodes use the moth caterpillar’s body to reproduce until there is none left of them. If you also need to remove any leatherjackets from your garden, be sure to use nematodes.

Nematodes are supplied as a powder, which, when mixed with water, is applied to the box plant using a watering can. They should be applied correctly to be effective, as they are UV and drought-sensitive. To get the best results, apply them in the evening when the temperatures are above 12C and the conditions are moist.

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Chemical insecticides

We do not recommend using chemical sprays as they can harm pollinators and other beneficial insects and animals. However, if you still choose to use them, make sure to spray only the young caterpillars. Thanks to their shroud of webbing, box tree caterpillars are very good at protecting themselves. So a lot of spraying is necessary to penetrate the webbing. You might be better off removing them manually.

There are many answers to the question “How to kill box tree caterpillars?” still, the best prevention method is to regularly check every plant you bring home.

Are box tree caterpillars poisonous to humans?

Box tree caterpillars may appear harmless, but they can be toxic to humans. The hairs on the skin of caterpillars can sting or irritate bare hands when touched. The fluids released by some caterpillars can be poisonous.


  • Box tree caterpillars are greedy creatures who can completely defoliate a hedge within days.
  • Box trees can survive the invasion as long as the caterpillars don’t eat the bark of the main stems.
  • The pupae can easily survive up to -30 degrees in cold seasons.


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