Last week I found this beautiful, multi-coloured metallic Beetle crawling on a Rosemary in our garden. This is Chrysolina americana, also known as the 'Rosemary Beetle'. Actually it isn't just found on Rosemary. It is also seen on other herbs such as Lavender, Sage and Thyme.
Unfortunately this beetle is a garden pest. At this time of year (mid-Summer) it simply sits on its host plant and does little damage. However, later in Summer feeding increases, they mate and eggs are laid. Larvae emerge from the eggs around ten days later and they, together with the adults, eat your herbs!
There currently is no predator you can introduce to dispose of Rosemary Beetle. If you want to go chemical-free the only option is to remove them by hand. You can also spray with a range of chemicals ranging from organic (Pyrethrum, derived from Chrysanthemum leaves) to non-organic solutions. Because herbs are edible plants please think carefully before spraying and do NOT spray with any systemic insecticide if you intend to consume them!
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