Box tree moth: life cycle, identification & treatment

Kati
Kati
Kati
Kati

I am a qualified gardener and horticulturalist and love everything that grows! Whether it's a shrub, a tree, a useful plant or a supposed weed: for me, every plant is a little miracle.
In the garden I look after my 13 chickens, grow fruit & vegetables and otherwise observe how nature manages and shapes itself.

Favourite fruit: Blueberry, apple
Favourite vegetables: Braised cucumber, kale, green pepper

Learn everything you need to know about box caterpillar identification and treatment to inhibit infestation of the voracious box tree moth and its caterpillars.

Box caterpillar in bush
Caterpillars of the box tree moth can cause a lot of damage [Photo: Eileen Kumpf/ Shutterstock.com]

Did you notice any discoloured leaves, dead branches, white webs and caterpillars on your box tree (Buxus) – or did you observe these symptoms in the neighbourhood? They possibly point to an infestation of the infamous box tree moth (Cydalima perspectalis). Now is the time to inform yourself and act fast in order to minimise box tree caterpillar damage on your shrubs.

The box tree moth or box hedge moth is an invasive species from East Asia. It was introduced to Central Europe a few years ago and it specialises in box trees, which in many areas led to a complete devastation of the evergreen shrubs. This article will give you a brief overview of the box tree moth: what is the active season in the year, how do you recognise box tree moths and how to effectively treat it either chemically or naturally.

Box tree moth: a life cycle in a year

The problem with box tree moths is that it leads a rather hidden existence. The moths are nocturnal, so laying eggs goes unnoticed – unless you use a pheromone trap. Check out the table below this paragraph to see the development of the moth in the course of the year. Unfortunately, you cannot rely on the time periods stated because speed of larval development is, among other things, temperature-dependent. A very mild or cold spring can cause development of box caterpillars to be early or late by several weeks. Observation of moth flight via traps and regular control of your shrubs between March and September is therefore unfortunately the only possible and reliable way to notice the start of an outbreak in time.

MonthAprilMayJuneJulyAugustSeptember
Developmental stageCaterpillars (overwinter)Caterpillars (overwinter)
Cocoons
Moths, eggsEggs, caterpillarsCocoons, mothsMoths, caterpillars, eggs
GenerationLast year’s generationGeneration 1Generation 2
Box Tree Moth Trap
Box Tree Moth Trap
star-placeholder star-placeholder star-placeholder star-placeholder star-placeholder
star-rating star-rating star-rating star-rating star-rating
(5/5)
  • Reusable pheromone trap for monitoring box tree moth activity
  • For the early detection of infestations - covers an area of up to 180m2
  • 100% insecticide-free - not harmful to humans or pets
£24.99

How to recognise the box tree moth

Fortunately, it is possible to detect the moth long before branches turn into yellow dead wood. You will find yellowish box tree moth eggs located in the outer rims of the box tree in densely packed formations. Later, the larvae, just a few millimetres in size, will hatch from them. They are light green-yellow in colour with a typical black head. Immediately after hatching, they make their way to the protected areas inside the shrub to hide in webs and eat the poisonous boxwood leaves. After several months, when the larvae have grown a little bigger , the colour changes. They become darker and the characteristic black and white pattern emerges. At this point, they emerge from the inside of the box tree and return to the outer parts of the shrub. After six larval stages, the box caterpillars pupate, hidden in webs and transform into moths. The adult box moth is usually light in colour. It will produce the next generation of ravenous caterpillars.

box hedging caterpillar
The pupa of boxwood caterpillars is also hidden in webs [Photo: AFPics/ Shutterstock.com]

Summary: How to identify box tree moths

  • Severe infestation leads to sections of branches dying off
  • You can recognise an infestation early on through indicators, such as webs and max. 5 cm long caterpillars; buxus caterpillars are green-yellow, later with black-and-white markings and white bristles; they have a characteristic black head
  • The eggs are yellowish, hanging in the outer shrub areas under the leaves
  • The approximately 4.5 cm long buxus moths are not always the same colour; but usually they are light with black wing edges

Getting rid of box tree moths

If you identified an infestation early on or if the population is small enough, we recommend reading this article on effective household remedies. It describes various interesting effective methods – such as using a strong jet of water from a garden hose – and less effective approaches – such as baking powder or algae lime.

However, if your situation is more severe and you are dealing with a rapidly dying box tree full of caterpillars, then your approach needs to be different. In that case it is time to make up your mind: are you looking for alternatives for the box tree or is your goal to eliminate the caterpillars? You can find out how to get rid of the box tree moth here. If you are not interested in treating the caterpillars with poison, you can find natural methods that achieve good results without chemicals. The use of nematodes, neem oil and preparations with Bacillus thuringiensis work amazingly and are yet gentle to the environment.

box bush caterpillar
Just touching box plant caterpillars is not poisonous [Photo: vvoe/ Shutterstock.com]

Tip: You do not have to be afraid of touching box moth caterpillars. The caterpillars are not harmful to the skin. But you should not eat them – and wash your hands diligently after handling them. The animals contain several toxic compounds which they absorb from the poisonous box tree.

When is the best time to treat the box tree moth?

The right time of treatment is essential for success. For example, applying a spray onto the caterpillars when they are still wrapped in leaves, will have no effect whatsoever. The same goes for boxwood eggs and cocoons. But when to use the spray or other remedies to treat the moth? This article will explain when the perfect time to treat the box tree moth is.

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