Berberis sawfly

Berberis sawfly became established in south-east England in about 2000. It has since spread throughout most of England. It is the only insect that feeds on Berberis, likely to cause severe defoliation.

Berberis sawfly larvae.

Berberis sawfly larvae.

Quick facts

Common name Berberis sawfly
Latin name Arge berberidis
Plants affected Berberis, especially B. thunbergii, and Mahonia
Main symptoms Leaves are eaten by caterpillar-like larvae. Plants may be completely defoliated
Caused by Caterpillar-like larvae of a sawfly
Timing May-October

What is berberis sawfly?

Sawflies are in the same group of insects as bees, ants and wasps (the Hymenoptera). They have caterpillar like larvae that feed on plants the adults are winged insects that can appear fly like.

Berberis sawfly has creamy white, spotted larvae with black heads. They feed on the foliage of Berberis and Mahonia and can cause severe defoliation. This species of sawfly will only feed on these two plants.



Seen berberis sawfly? We would like to know.

As part of our research the RHS would like to know where berberis sawfly has been seen.

Please submit your records via our berberis sawfly survey (expected time to complete survey = two minutes).

Submissions to our pest and disease surveys are stored permanently in an anonymised form in order to monitor the spread of the pest or disease. We may contact you within 2 months of your submission in order to verify your sighting but your personal data will not be permanently stored in connection with your submission and will be deleted after 1 year. We publish and share only non-identifiable data from survey submissions (such as a six figure grid reference) with third parties and the public for the purposes of scientific research and advancing understanding among gardeners.

Thank you to everyone who has submitted records so far – read a blog about the surveys 

Watch an animated map of the results from the berberis sawfly survey (links to YouTube) 


Plants with by berberis sawfly are easy to spot:

  • Branches or the whole plant can be defoliated, berberis sawfly is the only insect likely to cause such severe defoliation
  • On closer inspection, black-headed, creamy white caterpillar-like larvae with black spots and orange yellow blotches may be seen feeding on the foliage
  • The adults are shiny black insects, up to 8mm long, with greyish-black wings. They appear similar to many other species of sawfly
  • Sawfly larvae on plants other than Berberis or Mahonia will be a different species, see links below for other common garden sawflies


Non-pesticide control

  • Check plants regularly between late April and October for the presence of larvae and remove by hand if feasible
  • If a plant is repeatedly defoliated consider replacement with a non-susceptible alternative

Pesticide control

  • If numbers of larvae are too high for hand picking, control may be achieved by spraying with pesticides. Spaying at dusk is likely to give the best results
  • Organic contact insecticides containing natural pyrethrins (e.g. Bug Clear Gun for Fruit & Veg, Ecofective Bug Killer). Several applications of these short persistence products may be necessary to give good control
  • More persistent contact insecticides include the synthetic pyrethroids lambda-cyhalothrin (e.g. Westland Resolva Pest Killer), deltamethrin (e.g. Provanto Ultimate Fruit & Vegetable Bug Killer) and cypermethrin (e.g. Py Bug Killer)
  • The systemic neonicotinoid insecticide acetamiprid (e.g. Bug Clear Ultra) is also available
  • Follow label instructions when using pesticides
  • Plants in flower should not be sprayed due to the danger to pollinating insects
  • Inclusion of a pesticide product does not indicate a recommendation or endorsement by the RHS. It is a list of products currently available to the home gardener


Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)


There are two generations of berberis sawfly during the summer and there may be a third generation in autumn.

The adult sawflies are 7-9mm long and are shiny black with darkened wings. The antennae are swept upwards.

Eggs are inserted under the epidermis on the underside of leaves in batches of up to seven. These hatch into caterpillar-like larvae that proceed to devour the foliage.

When fully grown the larvae are up to 18mm long. They go into the soil to pupate within silk cocoons. This insect overwinters in the ground as pupae.

Gardeners' calendar

Advice from the RHS

Find out what to do this month with our gardeners' calendar

Advice from the RHS

Did you find the advice you needed?

RHS members can get exclusive individual advice from the RHS Gardening Advice team.

Join the RHS now

Get involved

We're a UK charity established to share the best in gardening. We want to enrich everyone's life through plants, and make the UK a greener and more beautiful place.