ABC Wednesday 4: V is For...
... Viburnum Beetle
Just before we went on holiday my friend L emailed me with the following question:
...my guelder rose [aka Viburnum opulus - VP] is being eaten by small black and white caterpillars, about 5mm long. Not that I mind particularly but they are making a good job of turning the leaves into skeletons and I’d be interested to know what they might turn into, and if I might care then. I’ve had a quick look on t’internet but can’t find it. Any ideas?
My reply was:
I hope they aren't Viburnum Beetle:
The larvae do the damage, not the adults. My Vibunum tinus leaves are like lace and I'm going to replace it soon because the damage is that bad.
You've guessed what came next haven't you - it is indeed Viburnum beetle (Pyrrhalta viburni) that's doing the damage. The picture's of my Viburnum tinus 'Eve Price' showing the early signs of the beetle's presence - the badly damaged parts are currently swathed with Clematis 'Rouge Cardinal' and C. 'John Paul II', so I can't show you a 'lace' example. The link will take you to Cornell University's factsheet which has lots more information and pictures of both leaf damage and the tiny beetle larvae.
My Viburnum x bodnantense 'Dawn' which touches V. 'Eve Price' never gets attacked, nor does my Viburnum davidii a little further down the same bed. This fits with the observations reported in the Cornell factsheet which puts these two species into the 'Highly resistant' category. Viburnum opulus is in the 'Most susceptible' one, with most plants being destroyed in 2-3 years if the beetle isn't controlled in some way. The organic solution is to encourage natural predators such as ladybirds and to pick off the larvae by hand. Viburnum tinus is in the 'Least susceptible' category which means plants should recover from attacks. I've found this to be true, but flowering tends to be much reduced. With two other Viburnums in my garden, I feel I can safely get rid of it - once the Clematis stop flowering - and plant something new and exciting in its place, without seriously affecting the winter interest in my garden.
BTW L's partner writes Diary Of a Novice Bee Keeper and has lots of exciting news on the bee keeping front at the moment. Well worth a look.
For a Veritable cacophony of posts on the theme of V, do consult the ABC Wednesday blog.