Found in my garden recently, devouring the rosemary
Chrysolina Americana, more commonly known as the rosemary beetle, is an attractive, 8mm long, metallic green beetle with purple stripes. The larvae are grey with darker stripes and up to 8mm in length. It can be found feeding on the leaves of rosemary, lavender and related plants. Rosemary beetle adults remain relatively inactive on their host plants during July and August. In late August and September the beetles resume feeding, mate and lay eggs, which they continue to do on warm winter days until spring. The eggs hatch within two weeks and the larvae feed for as little as three weeks before entering the soil to pupate. The pupal stage lasts for a further two to three weeks before adults emerge.
The rosemary beetle was first found living out of doors in the UK at RHS Garden Wisley, Surrey in 1994 but this population soon died out and it was not seen again at Wisley until 2003. By 1998 established colonies of the beetle had been discovered near London’s Waterloo Station and Winnersh, near Reading, Berkshire.
In 1999 the first enquiry concerning rosemary beetle was received by the RHS Members’ Advisory Service from a garden in Weybridge, Surrey. By the end of 2005 the beetle had become widespread throughout London and surrounding areas, and had become one of the top 10 most frequent pest enquiries made to the RHS Members’ Advisory Service. The rosemary beetle is now widespread in England and has been found in parts of Scotland, Wales, Northern Ireland and the Irish Republic.