What can I do about Rosemary Leaf Beetles?

Question

They've ruined my rosemary bush and have started to spread to the sage.

Answer 1

This is copied from the UK Royal Horticultural Society - RHS site:

'Rosemary beetle can be controlled either with insecticides or hand picking of adults and larvae. If pesticides are used then these are best applied in late summer to early autumn or in the spring, when the beetles and larvae are active on the plants. Suitable insecticides that can be used include bifenthrin, thiocloprid or imidacloprid. Insecticides should not be used while plants are in flower because of the danger to bees. Only the ready-to-use formulation of thiocloprid (Provado Ultimate Bug Killer Ready to Use) is approved for use on edible herbs.'

They're becoming a growing nuisance in the UK, after spreading in from the continent.

I don't have them, and my Rosemary plants are fine. I don't know whether diluted washing up liquid will work, or other soap based insecticides. These are not poisonous killers, and just kill on contact -always beware of beneficial insects, including ladybirds, bees and lacewings though. A word of warning, a detergent, like washing up liquid, can be harmful to plants! The manufactured soaps for this purpose, are relatively cheap and available from most garden centres etc. But, I have no experience using them on this beetle - the effect works typically on all insects though.

Good luck! Rob

Answer 2

Try sprinkling some ashes on your rosemary and sage leaves. A friend told me to do that to my potatoes to take care of the potato flea beatles or flea beatles as they are called. It is probably the same kind of beatle just eating on different plants. The ashes can be washed off and it's not like it would hurt you if you ingested any as compared with chemical products.