Rosemary leaf beetle

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Posted: Tuesday 22 May 2012
by Richard Jones

The rosemary beetle is so deliciously beautiful, how could it possibly be considered a garden pest?

I’ve always been rather blasé about the rosemary leaf beetle, Chrysolina americana. It’s a splendid-looking beast with its metallic red and green striped dome of a body. The only other thing like it in Britain is the ultra-rare Chrysolina cerealis, known only from a few plants of stunted thyme clinging to the precipitous scree sides of Mount Snowdon. The rosemary beetle is so deliciously beautiful, how could it possibly be considered a garden pest?

I may have to eat my words now. Last weekend I found them nibbling my sage leaves. Sage is a staple in the Jones kitchen; I’ve taken to making my own faux pesto with it, or sticking in a few leaves whenever there is a chicken, sausage or pork recipe on the menu. It was whilst plucking a few leaves for the costolette di maiale con salvia (pork chops with sage) that I noticed the tell-tale black pellets of frass (caterpillar droppings) dotting the greenery. And, of course, there were the beetles, and the nibbled edges of the leaves suddenly became obvious.

I dare not mention my rosemary twig. The plant (it can’t possibly be called a bush) has become pot-bound, and has reached the stage where it is little more than a woody brush with a handful of stunted green twists that might, or might not, be leaves. Disgraceful, I know. Yet, here too, is a rosemary leaf beetle, trying to finish off my appalling anti-husbandry.

Rather hastily, I have re-potted said rosemary, in the hope that it recovers, and have translocated the lone beetle to the sage. I’m going to be a bit over-protective of the rosemary until it reaches a reasonable size. In the mean time I am happy to share my Salvia officinalis, but I must remember to knock off any beetles and their droppings before I cook.

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oldchippy 25/05/2012 at 10:57

Hi Richard,Last night I had the door open to the garden with the light on,There was a thud on the floor,On inspection I found a Cock Chafer laying on it's back,I haven't seen one before,They are very beautiful looking beetle's for there size not at all aggressive.The room was full of flying insect's.It must be the warm weather.

Oldchippy.

happymarion 27/05/2012 at 10:14

Still to see a rosemary beetle in Bristol, Richard, and my garden has many large rosemary bushes and sage bushes in it.Do you know if their range has spread to the West Country yet? I have not heard that any gardeners here have had trouble. Usually the loss of rosemary bushes is put down to a harsh winter like we had year before last.

@courtyardgarden 01/06/2012 at 18:46

I am overrun with them. They seem much keener on the sage than my thyme (even though they're planted in the same large pot). I had noticed it was nibbled for ages, but didn't worry too much about it - but last week I went out and the plant was half dead with 20+ beetles sunning themselves on it. Ugh.

I'm afraid I'm now squishing them if I see them, without spending time on a major hunt.

They are gorgeous, and I don't mind a few, but I draw the line when they start to kill things!

Lindsay4 08/07/2012 at 20:50

So pleased to identify this lovely beetle from my brief description typed into google!

Discovered them on my Lavender bush this evening when coming back from my evening stroll with my two cats. The nightly walks always throw up something interesting but I was especially happy to see something new to me.

Not worried about them having a chomp as the bush is very large and at least they are prettier than the darned slugs. I live in Poulton-Le-Fylde near Blackpool, so don't know if they are common round here.