Saturday, 9 September 2017

What's eating my viburnum and what can I do?

Viburnum beetle Green Fingered Blog
If you have a viburnum with leaves full of holes, this is the most likely culprit! The viburnum beetle. But what can you do about it? Well I may have identified their weakness...

WARNING! This post has a gruesome end. Why not tell me about the gruesome jobs that need doing in your garden? Leave a comment - it might make you feel better.

Viburnum bodnantense "Dawn" Green Fingered Blog
Viburnum bodnantense "Dawn"
There are lots of varieties of viburnum. If you don't have one in your garden there is probably one nearby. They are very useful shrubs. Some are evergreen and can be used as hedges or structural features (Viburnum tinus), while others have highly fragrant flowers on bare stems in winter (Vib. bodnantense "Dawn").  They can be grown as specimens in pots, as feature plants in a border, or as part of a woodland garden. They can provide flowers as well as foliage and autumn colour.  
Damaged Viburnum tinus leaves Green Fingered Blog
Damaged Viburnum tinus leaves 
Viburnums don't tend to get eaten by slugs and snails, but the viburnum beetle causes lots of damage that makes the plants look pretty terrible. It seems to affect some varieties more than others, like my V. tinus. The leaves end up full of holes, looking distinctly unwell, and the worst affected parts will be almost completely destroyed.
Viburnum macrophyllum Autumn Magic Green Fingered Blog
New growth on Viburnum macrophyllum "Autumn Magic"
It doesn't actually seem to harm or inhibit the plant, it's mainly cosmetic. You can cut off the ugly foliage and give the plant a feed to encourage it to produce fresh shoots. My Viburnum macrophyllum has produced nice glossy new leaves and flower buds. Cutting back and feeding works because there are two main times a year when viburnum beetles do their damage. You can spray insecticide but I prefer not to. There are other insects that feed on them, so encouraging them with bug hotels and wildlife areas may help.  But for an even simpler, though more gruesome solution, here's what you need to know about viburnum beetles:
The young beetle larvae emerge from the soil in spring and munch their way through your plants. They pupate and emerge as adults in August and start eating your plants all over again. After mating, the females lay a load of eggs, storing up more problems for the following spring. Their weakness is that when it comes to mating they are quite the sun loving exhibitionists of the insect world. There's nothing they love more than shagging in the sun! Nowhere to be seen on an overcast day, when the sun is out, look over your viburnum and there they all are, in pairs, in broad daylight.
Yes my photo at the top of this post might suggest otherwise, but they are almost always in amorous positions on top of the highest leaves, basking in the sun, as well as in each other! At which point, you can be the ultimate killjoy and squish them with your fingers two at a time. Not that pleasant, and perhaps rather cruel, but that's nature for you, and sometimes we need to intervene to balance things up. I don't advocate wiping viburnum beetles out altogether, and this method certainly won't do that, but the more you get rid of, the fewer there will be hatching next spring, and the better the viburnums will look.
That wasn't too gruesome was it? Leave a comment with your gruesome garden jobs - get them off your chest! I'd like to read about them - I'm kind of weird like that :)
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