Posted: 12 July 2023
Author: Luke
A growing number of Buxus (Box) Trees have been affected by Box Tree Caterpillars and subsequently Moths this year. It takes commitment to successfully rid your Buxus of this pest, and will need further treatment to prevent them in the future.
Initial Signs
It’s best to start watching out for signs of the caterpillars in the Spring, you will start to notice tight cobwebbing inside the plant and this is where the caterpillar tends to hide. There are a few cycles throughout the year, with different generations of caterpillar and moth overlapping one another, as they keep feeding and laying eggs. They overwinter inside the Buxus too, so keep an eye out during the Autumn as this is when they may start to web together – they’re preparing for Spring! The moths tend to choose lovely, previously unaffected box plants to lay their eggs in.
Treatment
Treat the Buxus with a pesticide such as Bug Clear. It’s best to reapply every two to three weeks between March and October for optimum results. Even if you start slightly later than March, there is still the potential to catch the second cycle. Caterpillars will be killed in the first application, but their eggs unfortunately remain unaffected. This means that without further application, after a couple of weeks all of the caterpillars will be hatching and beginning to eat the Buxus again.
Box Caterpillars are sneaky pests, who can hide within the foliage of the Buxus very effectively, so be sure to target the more difficult to reach areas within your Buxus for the best results.
Box Moth Traps
Box Moth Traps are great for monitoring caterpillar numbers, and can give you an indication of how bad the infestation is. Box Moth Traps use pheromones that attract Male caterpillars into the trap, so will go some way toward preventing reproduction in small infestations, but for larger infestations they will not be an effective solution.
Looking out for Box Moths will help you identify whether the eggs have been laid, before you even see the initial webbing – The moth itself has white or light brown, iridescent wings. It’s the moth that will lay the eggs and lead to the feasting caterpillars.
Removal and Replacement with Ilex Crenata
Unfortunately Buxus Caterpillars are here to stay after establishing themselves in Europe just over 15 years ago. Meaning that any Buxus you have will likely need to be treated each year moving forward. In light of this, most gardeners are choosing to replace their Buxus with more pest and disease resistant plants.
If your Buxus now looks something like this, unfortunately it’s unlikely to recover.
A great alternative to box hedges is Ilex Crenata, with a similar colour, growth rate and leaf shape, you can achieve the same modern look. Ilex Crenata is available in a variety of shapes and sizes, and is equally effective as a hedging or topiary shrub.
More tips for Buxus care and maintenance:
Being aware of Blight
Keep an eye out for any die back during the summer, particularly if we have a humid one as this can be a sign of blight. The best way to combat this is to create airflow through the plant, remove any fallen leaves that have made its way into the plant, and add mulch at the base to reduce rain splash back. If your Buxus has become affected by blight, which is fungus spots on the underside of the leaves, it’s best to cut out any affected areas.
General Maintenance
The best time of year for trimming your box hedge is during August, this will help to maintain the desired sharp edges. Feeding with a liquid feed, especially if your box hedge is in a pot, will help replace any depleted nutrients and help to maintain the dark, glossy leaves.