The Boxwood Moth ( Cydalima perspectalis) isn’t something I have encountered yet but I always feel forearmed is far better than being caught with my trousers down! This little moth is a native of Eastern Asia and was first found in Germany in 2006, thought to been brought in on a moved plant, since then it has spread around Europe, reaching the Uk in 2008, although it wasn’t until 2011, it started breeding. At the moment, most of the problem areas are around London and into the Home Counties surrounding London. It won’t be too long until it spreads further.
Again it’s not the moth that’s the problem but the caterpillars it produces, they love to feed on the leaves of Buxus plants, the type used in low hedges and topiary. They can strip a plant bare in days and due to the density of the tightly clipped hedges and topiary, can indeed be hard to treat.
The adults have a windspan of 4cm wide and can be found in two forms here in the uk
They lay yellow flattish eggs on the underside of the leaves on Buxus plants and it’s not long until the yellowish green caterpillars hatch and grow up to 4cm.They cover the plant with a dense webbing as well
I recently attended the European Buxus and Topiary Society AGM at Hever Castle, where as you would expect, the subject is close to the EBTS hearts. Indeed the chairman, Chris Poole, has spent a lot of time looking into the problem, using the European arms of the society, to find out more of the ways they treat this pest in the rest of Europe.
There are two ways to find out they are in your area before finding out they are the hard way!
The first one is to set a trap for them using a pheromone lure that attracts the males to the trap. This lets you know that they are in the area and how dense the population is. The best lure to use is Ginko Buxux lure that lasts for about 240 days and this is a available from Green Gardener. It is mainly a monitoring method but by removing some of the male moths, it at least reduces the amount that will reproduce.
The second way is a great idea from the EBTS and that’s a online monitoring map. This interactive map is very easy to use and add your own findings on. It does depend on people using it so the more the merrier! It lets you know where and then the moths and caterpillars have been spotted so you can keep a closer eye out for the little blighters. To add your own observations and to take a look at the map, click here.
Once you know you have it, treating it can be slightly problematic, with the thick webbing and the dense foliage of Buxus stoping the chemical reaching the caterpillar. However new in the uk for 2018, Topbuxus have released a biological control called XenTari®. XenTari® uses a microorganism called Bacillus thuringiensis subspecies aizawai. XenTari® is sprayed onto the foliage of the plant covering both surfaces of the leaves. When the caterpillars eat the leaves, the cry proteins damage the gut of the caterpillar, this allows the microorganism to spread around the caterpillar and kills off the caterpillar. They normally stop eating the Buxus within an hour but they take up 1-3 days to die. 1gram dissolved into a litre of water covers about 10m2 of Buxus and lasts up to 2 weeks. It is available from TopBuxus
If you love Buxus, Yew or indeed any form of topiary in the garden, why not think about joining the European Buxus and Topiary Society. It costs just £25 per year for a single adult membership and for that you get all the up to date information on Buxus treatments, the yearly magazine Topiarus and the opportunity to visit some fantastic gardens while meeting some great likeminded people. No this isn’t a paid advert, I am a member myself :). For more information click here
Big thanks to the EBTS for the photos used in this blog. The chairman, Chris Poole is also available for talks on box blight and boxtree moth around London and within an hours drive of his Home in London