The Royal Horticultural Society (RHS) has been researching Chrysolina coerulans or blue mint beetle.
The pest was confirmed to be breeding in the country by the charity's entomology department when specimens were sent to them by an RHS member in Kent in July 2011.
"The beetle is widespread on mainland Europe and the detection of breeding adults in the UK could mean problems for gardeners who grow this herb," says Andrew Halstead, Principal Scientist Plant Health.
"It is therefore important that we find out if there are any other breeding adults elsewhere in the UK. The adults and the black, soft-bodied larvae both eat the foliage."
The 7mm long blue mint beetle is quite different in colour to our native beetle, the green mint beetle (Chrysolina herbacea) which is shiny, emerald-green.
This beetle also eats mint leaves but is generally not a problem because it occurs more frequently on wild mint.
"At the moment our control suggestions are the same both for our native green mint beetle and the new incomer," says Andrew.
"If there are only a few then removal of the beetle and larvae by hand works best."
For more information on control visit rhs.org.uk/biodiversity/blue-mint-beetle
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