Grubs in the Compost - Rose Chafers (Cétoine dorée)

I often see questions on forums aimed at English speakers now gardening in France about larvae they've found in pots or compost. I can understand why gardeners, especially those who have come from areas like the UK plagued by vine weevils, panic when they find enormous fat grubs in the pots of their prized plants. We've become so attuned to thinking that anything living in the controlled environment of our container-grown plants must be a threat (and vine weevils certainly are) it is understandable that we squash first and ask second. After all, these beasts are eating the roots of the plants, aren't they?

Well, no actually, in many cases they are not. The fat grub most commonly found in pots or compost heaps in my garden and many others are in fact the larvae of the rose chafer beetle. The grub is large, larger than that of the vine weevil, although the appearance is superficially similar. The rose chafer is an altogether chubbier chap and can curl right up. The smaller vine weevil tends to be more of a comma shape.
Should we worry about vine weevils? Absolutely, they eat the roots of plants in pots and that inevitably kills them. At night hunt for the adults on the foliage of your potted plants, especially the ones that have had the tell-tale notches taken out of them. The adults are deftly squashed underfoot. When repotting look for the grubs in pots and again dispose of them.

But the rose chafer grub does not eat your plant's roots but rather the compost they are living in. So yes, eventually the plant will suffer, so if you find them in a pot relocate them to the compost heap where they will work away making the stuff you will eventually put on your garden finer and more nutrient rich! And if you find them already in the compost heap, welcome them: they are turning your garden waste into compost for you.

Finally, enjoy this stunning green beetle as it bumbles around in flowers in the sunshine!