I’ve always had pelargoniums on the balcony. Common as muck they may be, but in full bloom they’re glorious. And with a bit of protection they will not only over-winter, and but also sometimes keep on flowering . If you were reading this blog a few years ago, you’ll know that I had one container of salmon-pink zonal pelargoniums that went on for two and half years - in all that time, even in January when it was wrapped up in fleece, there wasn’t! a moment when it wasn’t in bloom.
But each year it got progressively more difficult to keep them alive through the summer. And last year I lost the lot.
So this year I replaced them all. Zonals, ivy-leafed, regals …. Here they are in May this year…
And I’ve lost the lot again.
Why? Again if you’ve been reading regularly for a few years, you’ll guess. It’s this …
Cacyreus Marshalli, or the Geranium Bronze Butterfly. It’s always been a problem, but for the last couple of years it’s been impossible to keep the plants alive.
A quick recap for those of you who aren’t familiar with it. Native to S.Africa (as are pelargoniums), it was introduced to S. Europe about twenty years ago and has been spreading like wildfire ever since. It’s been in Italy since 1996, and is now posing a severe threat to commercial pelargonium cultivation - apart from anything else, because people are starting to avoid buying the plants, knowing they won’t survive.
Why does it do so much damage? The larvae of the butterfly don’t feed on the leaves. They burrow right into the stems and eat the plant from the inside out, killing it. If you can spot the tell-tale holes you can sometimes cut off the affected part - but over the season you frequently end up cutting back the whole plant.
And go away for a few weeks, like I always have to in the summer (…have to? Only a gardener could feel like that about a holiday ) and you come back to this …
What can be done about them? There don’t seem to be many organic options. One of the studies recommends the “natural” insecticide Bacillus thuringiensis Kurstaki - but don’t ask me where I’d get hold of it. (Wonder how many times longer than the bacteria the name is?) There is also an insect with the equally wonderful name of Macrolophus caliginosus Wagner, which feeds off the eggs and hatchling larvae - but ditto, and would it stay on the balcony anyway? Another source suggested companion planting. Highly aromatic plants like lavender, mint and thyme are supposed to discourage the butterfly. Well, I can try - but I have my doubts. By pure chance I did have mint growing fairly near the pelargoniums this year. Not close enough maybe …
Other than that, it seems there are only two choices - swamp the plants with noxious chemicals, or give up on pelargoniums all together. Don’t like the first, and don’t want to do the second. But it seems the only other option is to invite yet another massacre …
Useful Links
Lupi and Zucker, The butterfly cacyreus marshalli in Northern Italy and susceptibility of commercial cultivars of pelargonium.
Regione del Veneto,
Il licenide dei gerani
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