Home » Beetles » Have you seen a Hazelnut Weevil Curculio nucum hole?

Have you seen a Hazelnut Weevil Curculio nucum hole?

This is a species I have never seen though the distinctive holes it leaves in hazelnuts were a familiar sight in my childhood in Gwent when gathering nuts in the autumn. I know other coleopterists have encountered this species rarely or not at all and there is a general belief that it has declined severely. Presumably Grey Squirrels are to blame as they have increased in recent decades and most hazelnuts are now eaten by squirrels before they’ve ripened.

Curculio nucum exit holes

Has it declined? Was it ever common? Fowler (1891) referred to it as “local; generally distributed in the London district and the South of England …”, and Joy (1932) gave it as local. Roger Booth investigated this in 2003 by surveying some of the early beetle collections at the Natural History Museum. It is not always easy to interpret such sources but, for example, C.E. Tottenham recorded adults on 9 occasions in a 38-year period (1911 – 1949) totalling only 10 specimens. Roger concluded that the weevil never was very abundant.

Adult Curculio nucum © Roger Key

Nevertheless, it does look as though C. nucum is rarer now. It now seems to be a species that an active coleopterist will encounter about once in every 20 years (or less often than that in my case!).

So, I was really pleased to see lots of hazelnuts with holes in on the Isle of Wight on Monday (12th September). I picked up 141 hazelnuts of which 14 had C. nucum exit holes. The island is still free of Grey Squirrels and maybe the local Red Squirrels are less voracious in their appetite for hazelnuts?

We could get a much better idea of the current status of C. nucum by recording exit-holes in hazelnuts rather than looking for the adults on hazel bushes in May and June. I’m going to start keeping more of an eye out and I’d be interested to hear what others find.

The hole is made by the fully-grown larva as it exits the nut before overwintering in the ground where it will pupate in the following spring. I’ve brought some nuts home from the Isle of Wight in the slender hope that there may be some larvae still to emerge, and in the even more slender hope that I’ll be able to rear them through to adulthood in 2012.


27 Comments

  1. I found several hazel nuts with holes like this at Newbourne Springs, Suffolk last Saturday (10th Sept).

  2. I’ve encountered it three times in two years, but that was 1997-1998 in Berkshire, at a site with loads of hazel (and which used to have Cryptocephalus coryli as well). Not seen it since, and using your 20-year rule I won’t see it again in my lifetime 🙁

  3. Seth Gibson says:

    Do other species create similar exit holes, or are they 100% indicitive of C.nucum? Currently gathering lots of hazelnuts for small mammal identification purposes, and shall now be checking carefully for exit holes!

  4. We found quite few holes in nuts from a hazel coppice on The Whitchurch Millennnium Green, Winchester Street,Whitchurch Hampshire see our website.

  5. markgtelfer says:

    Graham Burgess emailed me on 6th October to say he’d just gathered 100 hazelnuts at Whitchurch, Hampshire and found 10 with holes in. 10% is the same proportion as I found on the Isle of Wight which suggests there is no effect of Grey Squirrels on weevil abundance. But more data needed.

  6. Mark,

    Whereabouts in Gwent did you find the weevil? I would be interested in relocating.

    Steve Williams

  7. markgtelfer says:

    Hi Steve, I lived in Langstone, near Newport, as a kid and would’ve collected hazelnuts just on footpaths around the village. Please let me know if you relocate.

  8. Roland Playford says:

    I live in SW France and have a marvellous crop of hazelnuts each year, collecting now. Perhaps 40-50 will have the exit holes.

  9. markgtelfer says:

    Thanks for the info Roland

  10. Gareth says:

    Hi Mark, This is an excellent website of yours. Hope you and Jo are doing well! I recorded some of these in Alton, Hampshire this year, maybe 10% here as well.

  11. markgtelfer says:

    Thanks for the info Gareth. It looks like there is no Grey Squirrel effect but I still think it would be a good research project for someone to do a careful comparison between the IoW and adjacent mainland.

  12. Richard says:

    I live in Brussels and an adult Curculio nucum flew into my flat last night.

  13. gilbert says:

    We just found holes like this in our garden. We live West Wickham, South Cambridgeshire.

  14. gilbert says:

    We just cracked open a hazelnut & fouand larva inside that had eaten up all the inside of the nut and was just about to come out!

  15. Richard Vaughan says:

    Have a Hazelnut tree in my garden in Fallingbostel germany with lots of the exit holes just like your picture.

  16. markgtelfer says:

    Thanks Gilbert and Richard, I saw a larva here in Bedfordshire on 11th August, inside a hazelnut. It had eaten nearly all the hazelnut so I guess they will be drilling their way out around now, as you’ve observed.

  17. Emmely says:

    Finally I know who is eating more than half of my nutharvest!
    North-West Spain seems to have no shortage of this sweet little weevil.
    Next question,what to do about them??’

  18. Robert says:

    Plenty of the damned holes in my hazel nuts here in Somerset between Wincanton and templecombe, and at least 3 grey squirrels here in the garden rejecting them and leaving them for me,!

  19. Meg Game says:

    I’m a grower of Kentish cobnuts, and I can hardly believe you think them declining! This year I have about one tonne of nuts, and about 30% are infected with nut weevil, a major pest in Kent and elsewhere where the nuts are grown. Many commercial nut orchards are sprayed for them – several sprays are permitted.

  20. John Viner says:

    I have a generous Hazel tree in my garden and, this year, have managed to save about 25% of the nuts from grey squirrel, which accounts for about 30% and the Weevil, whose larvae holes account for the rest!

  21. Fearless Jones says:

    Hi I have seen such holes in a few hazelnuts I picked up by a hedgerow in Brockweir , Gloucestershire today.

  22. markgtelfer says:

    Thanks to Emmely, Robert, Meg, John and Fearless for recent (and not so recent) comments. It’s becoming more and more of a struggle to pick through hundreds of spam comments for the genuine ones.

    I think with the information provided by so many people we can now say that the Hazelnut Weevil is common in much of southern Britain. If you look for holes in hazelnuts, the evidence is absolutely clear.

    However, despite that, adult Hazelnut Weevils are rarely seen and difficult to find. It is a paradox! And I’d still love to see an adult.

  23. Jonathan Bye says:

    I have found these holes in hazel nuts over several years and now I know what causes them hope to see the weevil this year. I live in the South Lincolnshire fens.
    Are the adult weevils nocturnal, do you think?
    Great website!

  24. markgtelfer says:

    Thanks Jonathan. I bet you’re right that the adults are nocturnal. But you’d think they could still be found by day by beating hazel branches over a beating tray.

  25. AndyfromDover says:

    hi i have a hazelnut tree and many of the nuts have these exit holes. The tree itself also has many similar hole all over the trunk and branches. Could these be from woodworm or some other insect that loves hazel?? the tree is pretty health still at the moment. Some thoughts on this would be helpful.

  26. markgtelfer says:

    Thanks Andy, there are numerous beetles that make holes in decaying wood of which The Woodworm is just one. Most are not very fussy about what species of tree/shrub they use and I don’t think there are any which specialise on Hazel.

  27. brian heppell says:

    i find it a little strange you want to propogate a hazelnut pest! At least 10% of the hazelnuts in my garden are infected with these weevil grubs. I know i am further away (eisenach germany ) but hazel nuts are food for a host of animals not only man

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