Part of my job as a professional gardener is to identify the pests, diseases and disorders that sadly afflict plants from time to time. At the end of May this year one of my customers drew my attention to her hedge which seemed to disappearing at a fairly rapid rate!
The hedge is comprised of Box, or Buxus sempervirens to give it its 'sunday name'. Any keen gardener will tell you that Box, for years a staple of classic British gardens, is now threatened by two un-related sources. The first is Box Blight, a fungal disease which causes bare patches and die-back. However, this wasn't the pattern I could see in my customer's hedge. Instead, the foliage (or what was left of it!) was still green and very much alive.
I began to suspect the problem might be the second threat to box hedging - the Box Tree Caterpillar. I began to tease apart the affected plants and sure enough the culprit was quickly found. (see photographs). The caterpillars are the larvae of the Box Tree Moth (Cydalima perspectalis). They aren't native to the British Isles and originate in East Asia. The first cases were reported in Europe in 2007 and it wasn't until 2011 that they were first discovered in private gardens, initially in the South East. Having identified the problem I was able to recommend an appropriate insecticide to the customer. It is concerning that this particular pest has now migrated to the North West and I recommend those with Box in their gardens to be vigilant and stop any defoliation before it become too severe. The RHS provide an excellent page suggesting a range of different treatments to deal with the problem:
This isn't a particularly pleasant topic but it's an important part of the service I provide. I hope this has been of interest.
UPDATE July 2023
I am delighted to add that a return visit to inspect the hedge two months later showed that the pesticide had worked, predation of the hedge was 'stopped in its tracks' and the plants are producing vigorous replacement shoots. However, the outcome could have been very different without timely intervention.
Photographs used with customer's permission.