- Box tree moth larvae feed on box plants and can cause extensive leaf loss when caterpillar numbers are high.
- Look for webbing, eaten leaves, bare stems and green caterpillar with distinctive black and white markings.
- Box tree caterpillar activity is commonly seen between March and October in UK gardens.
- Box moth traps can help monitor adult moth activity and indicate when moths are present around your box plants.
- Box moth nematodes can be applied directly to affected foliage when box tree caterpillar is actively feeding.
Box tree moth has become a familiar problem for gardeners growing box in the UK. The real damage comes from its caterpillar, which feeds amongst the foliage and can leave a previously dense box plant looking thin and stripped.
It is easy to miss the early stages. Damage often begins inside the plant, where caterpillar and webbing are partly hidden from view. By the time bare patches are obvious from a distance, feeding may already be well under way.
What Is Box Tree Moth?
Box tree moth is an insect originally from East Asia. It was first recorded in the UK around 2007 and has since spread, with the pest becoming particularly noticeable in southern England.
The adult moth usually has white wings edged with brown. It is the larval stage, however, that gardeners need to watch closely because the caterpillar feeds directly on box foliage.
Several generations can occur during a year. This means dealing with one period of caterpillar activity does not necessarily mean the plant will remain clear for the rest of the season.
How to Identify Box Tree Caterpillar
Young box tree caterpillar is green and yellow with a black head. As it matures, the markings become more distinctive, with black and white striping along the body.
Do not just inspect the outside of the plant. Part the branches and look through the centre of the box, especially where leaves appear damaged or stuck together with fine webbing.
In a real infestation, the webbing is often what catches your eye first. Look closer and you may find caterpillar tucked amongst it, along with partially eaten leaves and small areas of bare stem.
Signs of Box Tree Moth Damage on Box Plants
Webbing around leaves and shoots is one of the most recognisable signs of box tree caterpillar. You may also notice eaten leaves, brown or bare patches and, in severe cases, considerable defoliation.
Look closely and you may see caterpillars moving amongst the foliage or feeding within webbed sections of the plant.
Damage can be particularly noticeable on recently trimmed box, where there is less foliage to disguise affected areas.
When Is Box Tree Moth Active in the UK?
Box tree caterpillar is mainly active between March and October, although timing can vary depending on temperatures and seasonal conditions.
More than one generation can occur during the year, so an infestation that appears to have disappeared may return later in the season.
How to Check Box Plants for Box Tree Moth
Start by looking for pale, damaged or missing leaves, then gently separate the branches to inspect the centre of the plant.
Look particularly for webbing, leaves that have been drawn together and live caterpillars hidden within dense foliage.
If you have a long hedge or several box plants, inspect multiple areas rather than assuming the whole planting is clear after checking one section.
Using Box Moth Traps to Monitor Adult Moths
Gardening Naturally Box Moth Traps use a pheromone lure to attract male adult box tree moths.
Catching moths indicates that adults are active nearby and can help you determine when to pay closer attention to your plants.
The trap is designed for monitoring rather than controlling caterpillars, so it should be used alongside regular plant inspections.
How to Control Box Tree Moth Caterpillar
When active caterpillars are found, specialised box moth nematodes can be applied directly to the affected foliage between March and October.
These microscopic nematodes target the caterpillar and reproduce inside it before further nematodes are released.
Thorough coverage is important. Apply the solution directly to the foliage, including areas containing caterpillars and webbing. Dense growth may need to be gently opened to help the solution reach the affected areas.
Box tree caterpillars live and feed on the plant rather than in the soil, so applying nematodes around the roots will not target them.
Nematodes can be applied using the Gardening Naturally Nematode Applicator.
Box Moth Traps and Nematodes: What Is the Difference?
The two products target different stages of the box tree moth life cycle.
Box Moth Traps attract male adult moths and are used to monitor moth activity.
Box Tree Moth Nematodes target caterpillars and are applied directly to affected foliage.
Using traps for monitoring and nematodes when caterpillars are present provides a simple approach to identifying and managing box tree moth throughout its active season.
