A new phylloxera? – Just a bad dream…

Update 1.11.2018(30.10.2018)billn

Don’t worry, this was just a bad dream that I had one day. I’m sure it won’t happen in reality…

1Cydalima perspectalis – you may not know the name, you may also not know its more common name – the box moth – but its effect can be seen all over Europe. The box moth is not just a blight for gardeners, it is changing the Burgundy countryside, indeed the very environment too. Who knows what it is capable of.

I first noted one of these pretty moths in my Swiss garden in (roughly) 2008 or 2009 – I’d never seen one before. It was only in the following year than I noted its offspring eating my box-bushes and the ammoniacal smell of the caterpillars’ droppings. I didn’t think too much about it – insect population peaks come and go – but in this particular case the wave of insects simply grew and grew – the next year I lost a couple of small box-plants and all my larger ones needed remedial treatment. When I left in 2015, the new owner of my house didn’t treat – the box are now all gone.

So, where did this previously unseen aggressor come from?

Apparently this particular moth hails from Asia, where it has some natural predators. It was first identified in Germany in 2006 and has since spread throughout Europe – where it has no natural predators.

2In Germany’s Grenzarch-Whylen Nature Reserve, containing the largest box-tree forest in Germany, between 2009 and 2010, the caterpillars attacked all the box trees causing more than 90% de-foliation, nearly one-third of the trees lost all of their leaves. Although the population of moths then decreased, having eaten most of its food source, by 2012 the trees that had been fully defoliated died as their bark had also, to an extent, been eaten and thus exposed the trees to fungal infection.

Wandering in the hills of the Côte d’Or this summer, it was almost magical to see the woods so full of these ‘fairy’ moths – like a scene from Hollywood – except that all around was destruction of the boxwood brush that is characteristic of the unplanted areas of the Côte d’Or. 10 years ago, all was normal and you wouldn’t have seen a single one of these moths.

Whilst nobody would be interested in the whole-sale spraying of woodland in a Canute-like attempt to get rid of the moth, more formal plantings of box in gardens can be saved, but only with a regular application of insecticide or certain bacterium – it’s not easy because this moth, depending on the weather, can have at least three breeding cycles in one year. It looks like the boxwood brush of Département 21, and many other places too, after 1,000s of years, is to be lost. This got me idly thinking…

Dead and dying ornamental box-tree in Beaune’s Parc Bouzaise…

Adding 1+1 together to make, perhaps, 3 or more…
I well remember that in my Swiss garden were two similar trees – I think one male and one female – because only one of them would produce its orange berries at the end of each year. In most years, nothing would eat those berries, but in very cold winters – with consecutive days of lower than -10°C (less than 14°F), usually with snow on the ground, flocks of mistle thrush would fly in to eat the berries. I considered this (my) concept of the most palatable food available. By that I mean that if the ground was less hard and free of snow, these birds could always find something more palatable to eat. Put basically – these birds had to eat those orange berries or they would starve.

Now let’s just, non-scientifically, extrapolate that concept to these moths: What will happen, when all the box is gone? Will the moths die out? Or will they choose to live by eating something much less palatable to them than box-tree leaves? I’m quite sure that they will do the latter if they can.

Now what if that less palatable option turns out to be vines? Have we already met our new phylloxera but not yet recognised it?

[1] https://en.wikipedia.org/wiki/Cydalima_perspectalis

[2] John R, Schumacher J (2013) Der Buchsbaum-Zünsler (Cydalima perspectalis) im Grenzach-Wyhlener Buchswald – Invasionschronik und Monitoringergebnisse. Gesunde Pflanzen 65:1–6

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