I hadn't heard from them up until 2 years ago. They seem to be pretty 'new' - the first ones were spotted in the UK in 1994. So that means they've spread at warp speed.
They indeed kill the plants (rosemary, lavender, sage, thyme) because they eat the tender leaves.
You can see out plants have been nibbled on... and some stems have just dies. Such a shame...

I found a good artivle about them on Gardening Know How

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