How to get rid of box caterpillar

Box (buxus) has been grown in the UK since Roman times and is loved for topiary or neat hedging. However, a number of pests and diseases have attacked box in recent years making it harder to grow as hedges and topiary.

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How do I know that it's box caterpillar?

The box tree caterpillar, which can completely defoliate plants, originally affected plants in the south east of England, but it is spreading further. 

Webs on the leaves and greenish-yellow caterpillars are likely to be the first sign of attack. The caterpillars are 1.5-2cm long. You may also find pale-yellow, flat box caterpillar eggs on the undersides of the leaves. The box moth has a wingspan of around 4cm and the wings are white with a dark-brown border. 

You may have several attacks during the season, from April to October. 

Your plants should recover afterwards but will awful while they regrow new leaves. Quick treatment will halt the box moth life cycle and prevent further damage.

What is the best box caterpillar treatment?

The easiest method is to look for the greenish yellow caterpillars with black heads and pick them off to stop them feeding on box. Often their webs are the first sign of their presence. 

Also look out for pale yellow eggs on the underside of the leaves. Search deep inside the plant as you may find some caterpillars hiding there. Check the plant regularly from April to October.

The caterpillars can be sprayed with an insecticide recommended for box caterpillar, such as Bug Clear Ultra 2. 

You could try the biological control Nemasys Caterpillar Killer at the first sign of attack. This contains microscopic nematodes which are natural predators of box caterpillars. Infected caterpillars die turning yellow to light brown and become slimy when they die. The nematodes breed inside the caterpillar, releasing more nematodes into the surrounding area which go on to kill more caterpillars. 

You could also try a box tree pheromone trap to catch the male adult moths so they can't fertilise the female box tree moths to make eggs. It's also a way of monitoring when the moths are active in your garden so you can check plants for caterpillars.

Suppliers of biological control: Nematodes Direct; Green Gardener

Suppliers of pheromone traps: Dragonfli; Thompson & Morgan

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How to get rid of box blight

How do I recognise box blight?

This fungal disease is becoming increasingly common, causing unsightly bare patches and dieback in box. Common in rainy weather, two fungi cause the problem: both make the leaves turn brown, and one also leads to black streaks on young stems and dieback. You may also see white spores on the undersides of the leaves.

How do I treat box blight?

Bronze-coloured leaves can also be caused by a lack of potash, so it’s worth feeding with tomato feed before you take anymore drastic action to check whether it’s this, rather than box blight. 

If it is box blight, it’s often best to dig out and destroy any affected plants. However, if you’re keen to keep some of the plants, try cutting out the affected parts and picking up all the fallen leaves, plus the surface soil, underneath the plants.

There are no chemicals specifically recommended for use on box blight, but you could try a fungicide for ornamental plants.

How do I avoid box blight?

To help avoid the problem, try not to clip plants too often so they grow a bit looser and air can circulate easily. Also avoid growing other plants too close to them, and try not to get water on the plants when watering. It’s a good idea not to trim box when wet weather is forecast. Some varieties seem more blight-resistant than others, such as B. microphylla ‘Faulkner’ and B. microphylla var. japonica ‘National’.

Good secateurs are an eseential part of your garden toolkit. See our guide to the best secateurs to help you decide which pair to choose.

How to get rid of box sucker

What is box sucker?

Box sucker is a tiny insect, also known as a psyllid. It feeds by extracting sap from leaves, leading to distortion.

What damage does box sucker do?

Immature box suckers, or nymphs, feed on young shoot tips. They secrete chemicals into the plant which prevent the shoots developing properly — the leaves become curled and congested, looking like little Brussels sprouts on the shoot tips.

How do I recognise box sucker?

You need to look carefully among the leaves to see the insects themselves. The nymphs are pale green, less than 2mm long, and their bodies are flattened like a bed bug. You may also see patches of sticky honeydew, which often attracts sooty mould. The nymphs also produce quantities of a white, waxy secretion, which can accumulate on or around the plants.

What plants does box sucker attack?

Box sucker only attacks box plants. A different species of psyllid, apple sucker, attacks apple blossom, and other types of sucker can damage bay, elaeagnus and eucalyptus.

How serious is box sucker?

On regularly clipped plants the damaged shoot tips will normally be removed, so the damage is not serious. It can be more of a problem on young plants, or developing topiary, as the distorted shoots retard normal growth.

What is the life cycle of box sucker?

The sap-sucking nymphs are most abundant in April and May. They mature into winged adults from late April to June and eggs are laid on young stems in late summer. These overwinter and hatch the following spring.

How do I control a box-sucker attack?

On young plants, nip out damaged shoots as soon as they are seen. With older plants you can wait until normal clipping time. A second clip in late summer should remove most of the eggs. All clippings should be burned or binned, or put in a large-scale composting system, not your own compost heap.

Are there any suitable sprays for box sucker?

Products recommended for aphids should also help control psyllids if used in spring when the nymphs are feeding.  

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Alternatives to box hedge

If you’re fed up of dealing with this pest and other box problems, such as blight, it may be time to replace your plants.

Plants with small, evergreen leaves that can be used to make a low hedge or topiary like box, include: 

Euonymus japonicus ‘Green Spire’

Ligustrum delavayanum

Lonicera ligustrina var yunnanensis ‘Tidy Tips’

Podocarpus nivalis

Taxus baccata ‘Repandens’ 

Ilex crenata used to be recommended, but in practice it dislikes the dry summers and wet winters that are common in the UK.

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