Unfortunately, many of my customers have said that their box plants have been decimated by caterpillars this year.
But fear not if you have been hit by this plague of insects there is no need to take drastic action and dig up your box plants and burn them.
Your box will recover and the box tree caterpillars eating your plants are nowhere as problematic as box blight affecting them.
What Is A Box Tree Caterpillar?
The box tree caterpillar is a recent alien import to the UK and is the larvae of a moth that feeds on box plants (Buxus).
They are native to East Asia and the first report of the adult moth was in Kent in 2007.
It wouldn’t be until another four years in 2011 that the caterpillars would be first found in private gardens, where they are almost certain to have arrived in the UK via imported box plants.
At first, the problem was very localised but the caterpillar is becoming more widely established in England, and there have even been reports of it in Canada.
The box tree caterpillar has now been ranked the top garden pest in here in the UK by the RHS.
Have You Seen A Box Tree Moth?
The RHS is now conducting a survey to see where box tree moth has been spotted.
Submissions to the pest and disease survey are stored permanently in an anonymised form in order to monitor the spread of the pest or disease.
If you would like to submit findings to the survey please go over to the RHS website here.
Symptoms Of Box Tree Caterpillar
You are most likely to become aware of the problem when you spot the box tree caterpillar and its webbing on your box plants.
The female moth lays pale yellow eggs on the underside of box leaves.
A newly hatched caterpillar is greenish-yellow, with a blackhead. An older caterpillar can reach up to 1¼in (4cm) in length and has a greenish/yellow body with thick black and thin white stripes along the length of its body.
The pupae are concealed in a cocoon of white webbing spun among leaves and twigs.
The adult moth usually has white wings with a faintly iridescent brown border, although the wings can be completely brown or clear. The moth has a wingspan of around 1¼in (4cm).
The caterpillars eat box leaves and produce webbing over their feeding area. Plants may also show patches of dieback which may be especially apparent on trimmed plants.
How To Get Rid Of Box Tree Caterpillars
- Try to remove the caterpillars by hand if it is practical.
- If you need to treat a large affected area then you could try using a biological insecticide called XenTari created by TOPBUXUS.
- Pheromone traps which can help monitor adult moth activity.
- There have been reports of birds such as blue tits feeding on the caterpillars in some locations, but It is not yet clear if this predation will result in a reduction of caterpillar numbers.