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The rosemary beetle (Chrysolina americana) originates from southern Europe and has been found in Britain since the mid-1990s. The larvae and adults feed on the foliage of rosemary and related plants.
Rosemary beetle is an insect that eats the foliage and flowers of various aromatic plants, such as rosemary, lavender, sage, thyme and some other related plants.
Rosemary beetle has spread rapidly since first being found breeding in central London. It is now widespread throughout England and Wales. It is established in Scotland, present on Northern Ireland and may be established in parts of the Republic of Ireland.
Both the adult beetles and the larvae feed on the foliage and flowers of host plants, with most of the damage occurring between late summer and the spring. Heavily infested plants can look very shabby by spring. The plants' appearance will usually improve as new growth develops in late spring-summer.
Seen the rosemary beetle? We would like to know.
As part of RHS research we would like to know where the rosemary beetle has been seen.
Please submit your records via our rosemary beetle survey (expected time to complete survey = two minutes).
Submissions to our pest and disease surveys are stored permanently in an anonymised form in order to monitor the spread of the pest or disease. We may contact you within 2 months of your submission in order to verify your sighting but your personal data will not be permanently stored in connection with your submission and will be deleted after 1 year. We publish and share only non-identifiable data from survey submissions (such as a six figure grid reference) with third parties and the public for the purposes of scientific research and advancing understanding among gardeners.
Thank you to everyone who has submitted records – read a blog about the surveys
Watch an animated map of the results from the Rosemary beetle survey (links to YouTube)
Rosemary beetle and its damage are fairly easy to spot;
Host plants can survive light infestations without any noticeable adverse affects and so control is not always necessary
Hand picking can help to keep infestations below the level at which serious damage occurs. With the taller forms of rosemary and lavender, the beetles and larvae can be collected by tapping or shaking the branches over newspaper spread underneath the plant.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
During mid-summer rosemary beetle can be present on host plants as adult beetles that usually do little or no feeding. In late summer they commence feeding, mating and laying eggs. These hatch after about ten days and both adults and larvae will feed on the foliage throughout autumn to spring during periods of mild weather.
When fully fed, the larvae go into the soil to pupate. Adult rosemary beetles emerge from pupae in the soil in early summer. There is one generation a year but because the adults are long-lived, there can be some overlap between the new and old generations of adult beetles. Because of this, adult beetles can be found at almost any time of year.
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RHS statement on pesticides in horticulture
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