Berberis sawfly

A friend reported that her berberis had lost all its leaves. The few leaves remaining showed definite signs of having been eaten.

The culprit is undoubtedly the berberis sawfly, a pest new to the UK but spreading rapidly. Unhatched eggs may well have been carried in on an imported plant. Be that as it may, it is evidently here to stay.

The adult, a flighted black insect, lays its eggs on leaves, and it’s the emerging larvae that cause the damage. There can be two or three generations per year, so this can be a problem from May to October. If you grow berberis, keep a look out for grubs and squash them between finger and thumb. Otherwise, spray with an insecticide. The RHS website (where I found this image – delightful, is it not?) sensibly points out that you shouldn’t spray while the flowers are open because of the risk of harming pollinating insects – so this applies to spring only. Since berberis have finished flowering, zap the beasts immediately.

Larva of the berberis sawfly

Larva of the berberis sawfly

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2 Responses to “Berberis sawfly”

  1. David Price Says:

    Frightening! Just letting our berberis develop again after regularly cutting it back ruthlessly because it was near the children’s swing and I didn’t want them to impale themselves on the thorns. The swing is no more because the children are far too big for such things now. We’ll be looking out for the grubs.

  2. Andrew Mikolajski Says:

    Fortunately, berberis responds well to regular – and ruthless – pruning. I had another report that, after an initial attack, the grubs have now matured into sawflies and are now hovering around the regenerating bushes looking for a place to lay their eggs.
    I suggested replanting with conifers – this pest is here to stay.

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