Monday 15 June 2015

Rosemary Beetle - new to the garden

14th June 2015 - Topsham


As a change from counting Med Gulls and straining eyes to read colour rings on Blacke-headed Gulls and Sandwich Terns, I've been out and about with my macro lens. Here's a new beetle for the garden list - Chrysolina americana, commonly known as the Rosemary Beetle.

Chrysolina americana, on Bindweed Calystegia sp. - 12/6/2015 Topsham

Chrysolina americana, on Lavender Lavandula angustifolia - 14/6/2015 Topsham

I know neither of these are on Rosemary but they are right next to a Rosemary bush, these were just easier to photograph. With the name americana you might think this is a transatlantic import, in fact it comes from south and east Europe; the americana bit was attached by Linnaeus in 1758 and I can only guess he was mistaken as to the specimen's origin. It's pretty unmistakeable, up to 8mm long, a typical leaf beetle (Chrysomelidae) and very shiny with blue and purple/gold stripes; C.cerealis, the only similar native species, occurs only in Snowdonia.

The species was first found in Surrey in 1994, it's now all over south east England with a few records from the south west, it's also spread to Wales, Scotland and Ireland. It feeds on, not surprisingly, Rosemary and Lavender, but also related plants such as Sage and Thyme of the family Lamiaceae. The RHS class it as a pest so there's an argument for destroying it. On the other hand, if you're going to import and grow non-native plants you have to expect to deal with their associated fauna. There doesn't appear to be any evidence it will seriously affect native species. It's a beautiful thing and I think I'll just leave them be.

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