Strawberry blossom weevil – Anthonomus rubi

The diminutive Strawberry Blossom Weevil (Anthonomus rubi) with its oversized snout (or rostrum to be more correct) can play havoc with strawberries in an incredibly clever way.

The open flower is about 2cm across, the weevil (lower right corner) is about 2mm with an equally long snout
The open flower is about 2cm across, the weevil (lower right corner) is about 2mm with a snout almost as long again

The female weevil uses her snout to stab a hole into an unopened flower bud (that’s what she’s doing in the picture above). She then turns round and places an egg right into the hole and into the centre of the flower bud. Not content with that, she will then damage the stem below the bud, cutting off the sap supply.

This results in characteristic unopened flower buds that wither on their stalks. If you look very closely, you can often see the puncture marks on the bud where the weevil made her hole. Inside, will be the developing weevil grub.

Here's a closer view of the weevil on my thumb (complete with micropore as I'd sliced my thumb open. The micropore was quite handy as the weevil's feet were tangling in it and it kept it still long enough for me to snap it.
Here’s a closer view of the weevil on my thumb (complete with micropore as I’d sliced my thumb open). The micropore was quite handy as the weevil’s feet were tangling in it and it kept it still long enough for me to snap it.

These weevils also have a taste for raspberries and blackberries.

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4 thoughts on “Strawberry blossom weevil – Anthonomus rubi”

  1. I have an infestation of these in a patch in my back garden, starting to spread to my raspberries. I can’t seem to find any control for them. Do you have any suggestions?

    1. Hi Christine

      There is no specific treatment for strawberry blossom weevils.

      My first choice would always be a mechanical approach:if your fruit patch isn’t too large, you can remove the affected blossoms (to prevent the next generation of weevil developing) and pick off adult weevils that you find (to stop them laying more eggs).

      However, if you prefer, there are chemical control products available. But, because the larvae are inside the flower buds, they are protected from external applications of control products (be they “natural” or synthetic).

      There are systemic insecticides (insecticides that work by being taken up by the plant, rather than by having contact with the target insect) available for amateur/domestic use, e.g. Bayer’s bug killer. However, they are not specific and will also kill other insects. In addition, the active ingredients in many of these products are neonicotinoids and many garden centres no longer sell these products (because of concerns regarding honey bees).

      Because of the complexity of the situation regarding plant protection chemicals, I would recommend you ask at your local garden centre or nursery for advice on suitable products.

      Sorry that I can’t offer a more positive and simple solution!

      1. Thanks for your full reply. I have been picking off the affected buds over the past week or so, but likely will miss the odd one. I reckon I must have disposed of a good 70+ now, though there are many more unaffected ones still growing. My weevil kill score is 11, and I check each time I walk past, but they are tiny and I’m bound to miss a few.

        My patch is on it’s fourth year now, so in accordance with the advice in my gardening books I have been considering scrapping it after this season, and starting a new patch elsewhere. My only hesitation is that it is still very productive, and the plants still seem to be going very strong. It would take a good couple of years for a new patch to match this one in terms of productivity.

        What would your thoughts be, in view of the weevil problem too?

        Thanks!
        Christine.

      2. It would probably be a good idea to start another strawberry patch sooner rather than later, purely to keep productivity up. Strawberries will keep going for years and years if they aren’t knocked out by disease or a serious pest infestation, but yields will go down and down. Modern varieties have been developed to be fully productive from the first season and many commercial growers only use them for a single, or at most two seasons. With more traditional varieties, as you say – it will take a couple of years to get your new patch up to full production, so starting before the old one is exhausted is worthwhile.

        In terms of the weevils – it probably makes little difference: they will be in the soil/litter of your current patch, so they have a headstart in affecting the blossoms there, but they will quickly find the new patch too. What you’re doing is the best you can really – keep picking them off:)

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