Thanks for the heads-up Alisdair.
The boring activities would make branches more prone to breakage in the wind. I had a branch on an olive break last week, revealing a tunnel down the middle, which I presume was made by a leopard moth larva. Also, with Prunus especially, the exit holes will provide points of entry for various pathogens, such as silver leaf.
There are lots of species of longhorn beetle, and lots of those are pests. For instance, there is also an alert out in Britain for Asian Longhorn Beetle (ALB), Anoplophora glabripennis, which has already turned up in the USA and Britain -
http://www.forestry.gov.uk/pdf/expestalb.pdf/$file/expestalb.pdf.
And Japanese Cedar Longhorn Beetle, Callidiellum rufipenne -
http://www.massnrc.org/pests/pestFAQsheets/japanesecedarlonghorn.htmlDifferent places have different threats, depending on climate, the presence of suitable host trees, introduction pathway, etc.
General awareness of the threat from
multiple species of longhorn beetle is being raised by notices such as this -
http://www.pestalert.org/viewArchPestAlert.cfm?rid=27. ...Which points out 'Living longhorned beetles are increasingly being intercepted on commodities not covered under solid wood packing materials (SWPM) regulations. The importation of untreated commodities such as bamboo garden stakes, Christmas trees, and baskets may develop into high risk pathways for pest introduction.'
As well as introduced species, there are native ones.
In Cyprus, endemic longhorn beetles include:
- Agapanthia nicosiensis
- Purpuricenus nicocles
- Trichoferus antonioui
Other areas have their own wild species.
They all damage trees. Wild species tend to have reached a balance in their ecosystems, though sometimes it can be somewhat dynamic - in that population numbers may explode and crash as part of natural cycles. Introduced species run a greater risk of getting out of control because of lack/diminishment of natural predators and pathogens.
So, I would suggest being aware of longhorn beetles, and try to identify any adults you see, in case they are non-native species - which should be reported to local authorities. You may also come across the larvae in wood, but they are much harder to speciate, and fairly difficult to tell from the larvae of some other invertebrates (such as leopard moth).