How To Get Rid Of The Dreaded Box Moth Caterpillar

I have a love/hate relationship with Box, but not because the plants themselves are in any way annoying. Bless them, they’ve had a rough time in recent years with disease and pests. It’s these pesky fungi and critters that have become the bane of my life. However, help is at hand! Read on to find out how to get rid of the dreaded Box Moth Caterpillar the easy way.

If you’ve followed my blog and Instagram page @jpslifeandloves for a while, then you’ll know that in my last garden I had a box ball (Buxux Sempervirens) border, with over 40 different sized balls. In fact, one of my first blog posts ever was about the lush green balls of joy that us British folk seem to love so much. Find it here: I Do Love A Well-Trimmed Bush – All You Need To Know About Box!

At one point we had quite a bad infestation of Box Blight, which I managed to control with Top Buxus Health Mix. At the time, the RHS advice was to dig up all your Box plants and burn them. There was no way on God’s earth I was doing that! Top Buxus Health Mix literally saved my balls. I was distraught to the point of being reduced to tears at the thought of losing them. They were saved after a month or so of applying the mix and following the instructions to the letter. By the way, this article is not an advert for Top Buxus and I am in no way being paid to write this. Nor did I receive any free products. Just sayin’.

I plan to use Box again in our new garden and so far have just bought two medium sized balls for the front entrance. However, The other day I discovered signs of the dreaded Box Caterpillar.

Where did Box Caterpillar and Moth Come From?

Box tree caterpillars are the larvae of a rather pretty moth (Cydalima perspectalis) that feeds on Box plants. They are native to East Asia and were accidentally introduced to Europe in 2007. It wasn’t until 2011 that the larvae were reported in private gardens in the south of England. Now, they have been reported all over the UK.

The lifecycle lasts about 45 days. First eggs are laid on the underside of leaves and they are the colour of young Box leaves, so very difficult to spot and if you wear glasses you’ll definitely need them! After they hatch the Box Moth caterpillars develop large black heads and spots. It takes about 2 weeks to become an adult Caterpillar and they live for about 2 weeks.They form a cocoon in white webbing spun around the leaves and it takes a week for them to transform into a moth, where the cycle starts all over again, laying hundreds of eggs.

What Are The Signs Of An Infestation?

The first thing you will notice is that some of the leaves have been munched. On closer inspection you may see other leaves that have almost become a ghost of their former selves as they are nothing but a wafer thin see-through skeleton. Look more closely and you’ll start to see yellow-green caterpillars with black spots and a black head.

There will also be signs of webbing, silk strands all of over and inside the bush. The caterpillars tend to protect themselves within the webbing. You’ll see little tiny black balls too, they aren’t eggs, it’s caterpillar poo. I know, gross!

Left unchecked, these little green creepy crawlies will ravage your bush and it could even die. So, don’t delay, no one wants a ravaged bush!

Insecticide or Biological Warfare?

The first thing most gardeners will want to do is reach for the bug killer. There are various products on the open market, such as Provanto Ultimate Bug Killer. This will do something to help an infestation of Box Moth Caterpillar, but it’s going to cost you a small fortune in spray as you’ll have to keep doing it over and over and I’m pretty certain it won’t eradicate the problem. It’s very hard to get in and spray the underneath of all the leaves and even if you can you will be sure to kill all sorts of other insects by using it, potentially bees too!

So What’s The Answer?

The first thing I did was very time consuming, but worth it. Slowly and methodically go through the bush and remove any caterpillars you can see. I found over 100 of them! Either squish them or put them in a bucket of water. This will reduce the amount of immediate munching of the leaves and slow down the devastation.

The only product that controls box moth is Bacillus thuringiensis var Kurstaki, a natural bacterium often sold as DiPel or Lepinox. It’s not available for the average gardener because training is required to use it as it kills or moth and butterfly caterpillars if not used sparingly and only on the Box plant itself. However, Top Buxus have come to the rescue again with the introduction of Top Buxus XenTari.

When applied at the right moment, only 3 treatments per season are necessary to keep the caterpillar pest under control. The Box tree caterpillar goes through 3 cycles each season. Apply XenTari once every cycle at the moment when the first caterpillars are spotted. This moment can be more easily predicted by using a Box tree moth trap to monitor Box tree moth activity. When moths are trapped you can expect new caterpillars a couple of weeks later.

Be Careful Though!

You will need to be very careful to make sure you are not spraying any flowering plants nearby. I used a 3 litre backpack spray gun to save myself having to constantly keep pressing the gun, as it had a continuous spray mode. The backpack works by creating pressure inside the bottle using a hand pump. I also use the same backpack spray gun for when I’m applying Top Buxus Health Mix.

Each box of Top Buxus XenTari contains 5 sachets, each containing 3 gram of product. Dissolve the contents of 1 sachet in 3 Litres of water to treat 30 square meters of Boxwood surface. If you have less than 30 square metres then just leave the liquid in the backpack for the next treatment.

It does not harm important beneficial insects such as bees for pollination, insect predators, and parasites used in control of other insect pests. But, as I have said before, it can kill all forms of caterpillar, so, as long as you only spray your Box plants and nothing else, then it will only kill the caterpillars that eat the leaves of that plant.

I noticed the symptoms early, so the damage wasn’t too bad. Hopefully now I will be able to do the three treatments per year to stop the problem. I’m planning on there being many more Box plants in this garden, so here’s hoping.

I could, of course, choose a Box alternative such as Ilex Crenata or Euonymus Japonicus, but to me, nothing beats good old Buxus Sempervirens, even with all the problems!