This insect is a metallic green colour with purple stripes. It spreads very fast and can cause serious damage to aromatic plants if too many of them.
Both the beetles and its Larvae feeds on foliage and flowers of aromatic plants such as Lavender, Thymes, Rosemary, and other aromatic plants. This Beetle starts appearing in the month of June or early Summer as I found it on 7th June 2018 in our garden and the same day I took its picture as shown above.
How to eliminate Rosemary Beetle
Pick the beetle by hand if they are not too many, otherwise place the newspaper or piece of cloth under the plant and tap on the branches then collect them and get rid of them when they have fallen.
Although, this process will not eliminate them completely but it will keep the infestation to the minimum and prevent your plants from serious damage.
There are some pesticides for it but in my strong opinion, please do not use any pesticides because this could harm to pollinators and the other friendly and good insects too.