Box tree moth caterpillar (Cydalima perspectalis), also known as Box moth, Box tree moth and Buxus moth is an all-too-common pest of the humble box hedge, Buxus sempervirens.
So how does a professional gardener, here in Buckinghamshire, deal with it?
The first stage is identification. Chances are if you are reading this you have already identified it, but it’s worth knowing how to spot the difference between Box blight and the moth, as well as how to spot it before it becomes a real problem.
One of the key differences between blight and box moth is the distinctive spider web effect created by the caterpillars, as well as caterpillar droppings. Severe attacks can coat the entire hedge in spider webs, as shown below, and usually small greenish pellets (the caterpillars droppings) are found in the webs. Blight is more likely to show die off and bare stems without any of the above.
The moth is active between March and October, so what I do for my garden maintenance clients is between those months I do regular checks on the hedges. When walking past I will quickly run my fingers through and tease apart some of the hedges to look for caterpillars. Take a good look in there, particularly if you see even smaller spider webs, as this could be the beginning of an infestation.
There are other ways to identify these pests early, such as box moth pheromone traps. You might have seen them in botanical gardens, hanging from branches close to the hedging. I have had mixed results with them, but in gardens with a lot of box, or particularly sentimental box then it’s certainly worth a try. Keep a regular check on the traps – but not forgetting to physically check the hedge too! – so you can start treatment at the first sign of adult moths.
Once identified you can start treatment. The way I, and many professionals and botanic gardens I know control the caterpillar is to use a bacterium called ‘Bacillus thuringiensis’. Being a bacteria this is considered to be an organic solution. Before we go any further, you should understand a couple of things: Professionals applying any ‘pesticide’ or ‘herbicide’ products, even ones that can be bought off the shelf, MUST be licensed to use pesticides. This is the law in the UK. I hold a PA1/PA6 Use of Pesticides license. This is the required license for using these products in any kind of commercial or business setting. Having the license is great news for you as a customer, because not only does it give me the knowledge in applying these correctly to get the best results, but it also gives me the knowledge of how to apply them to keep YOU, your children, your dog, and your other non-target plants safe.
There is a product on the market that is available to home users to tackle box moth, however at the time of writing it has no approval in the UK, despite being widely available online.
Treatment is likely to not be a one-off. I regularly treat for it in the larger gardens I do garden maintenance for in Bucks. Depending on the severity of the attack, box can recover from the damage. I recommend feeding and mulching around the base of the hedge to help improve chances.
If you have box tree moth issues in your garden then please do get in touch today! I work throughout Buckinghamshire and offer a year-round garden maintenance service.