Box Tree Caterpillars: A Guide for Young Gardeners
What is a Box Tree Caterpillar?
Box tree caterpillars are the larvae (baby worms) of a moth called the box tree moth. They are a serious threat to box plants, which are commonly used for hedges and topiary (fancy plant sculptures). These caterpillars can completely eat the leaves of box plants, ruining their appearance and even killing them.
How to Identify Box Tree Caterpillars
Box tree caterpillars are easy to spot if you know what to look for. Here are some signs of an infestation:
- Webbing: The caterpillars cover parts of the plant with dense, white webbing, where they feed and hide.
- Dieback: Small patches of the plant may turn pale and papery, especially on newly trimmed plants.
- Caterpillars: Look for green/yellow caterpillars with black heads and stripes on their bodies. They can be up to 4 cm long.
- Droppings: You will see lots of pale yellow flakes, called frass, which are the caterpillars’ droppings.
- Pupae: You may notice white cocoons among the foliage, which are the caterpillars’ pupae (resting stage).
- Eggs: Small, pale yellow eggs can be found on the undersides of leaves.
- Moths: If you shake the plant, you may see brown or white moths with a wingspan of about 4 cm flying away.
How to Control Box Tree Caterpillars
There are several ways to control box tree caterpillars:
Organic Control:
- Hand removal: If you have a small infestation, you can remove the caterpillars by hand. Check the plant thoroughly every day and prune out any stems covered in webbing.
- Biological control: A micro-organism called Bacillus thuringiensis can be used to kill the caterpillars. This method is not available for home use in the UK and must be applied by professionals.
Chemical Control:
- Insecticides: Chemical sprays can be used to kill the caterpillars, but they can also harm other insects. Avoid spraying insecticides near flowering plants to protect pollinators.
Prevention:
- Pheromone traps: These traps release a scent that attracts male moths, disrupting their breeding cycle.
- Vigilance: Regularly inspect your box plants, especially deep inside and around the base, for signs of caterpillars.
Alternatives to Box
If you have lost plants to box tree caterpillars or are worried about future infestations, there are many alternative plants that you can grow instead:
- Box leafed holly: Looks similar to box and can be clipped in the same way.
- Lonicera nitida: Another good choice for hedges and topiary.
- Yew: A great alternative for hedging and topiary, but it is poisonous.
- Lavender: Attracts pollinators and has fragrant flowers.
- Mexican orange blossom: Also attracts pollinators with its flowers.
- Podocarpus: Has attractive variegated foliage.
- Euonymus fortunei: Has variegated foliage and fiery autumn colors.
- Euonymus japonicus: Another variegated foliage option.
- Berberis: Has fiery autumn foliage.
By following these tips, you can protect your box plants from box tree caterpillars and enjoy their beauty for years to come.
