Ash Sawflies active in the Belfast Area

Date published: 14 May 2021

Area of Expertise:

Ash sawflies are now active in the Belfast area. This is a relatively new species to Ireland. It was first recorded here in 2016, when severe defoliation was seen on ash trees in the Belvoir estate.

Sawfly larva on leaf

The ash sawfly is found in GB and whilst there can be sporadic damage to urban ash trees, the sawfly is usually a minor pest. However, we have seen regular defoliation of ash trees in the south Belfast area, in particular around Shaw’s Bridge and the Lagan towpath. The black sawflies emerge on mass and can be seen now congregating on ash branches, buds and emerging leaves.

defoliation of tree by sawfly infestation

The adult sawflies lay their eggs onto the emerging leaves and the resultant caterpillars are voracious feeders and can completely defoliate an ash tree. Thankfully, there is only one generation per year, and the affected ash trees recover later in the season. However, it is not known what effect the first defoliation has on the tree.

In AFBI, we are looking at the spread of this species, its impact, its relationship with ash dieback disease and whether it has any natural enemies. Naturally occurring parasitoids (parasitic wasps) serve as a regulating biological control in other parts of Europe.

Please log any sightings of ash sawfly on the TreeCheck web app, which is run jointly by DAFM and DAERA.

sawfly infestation at base of tree

For information on Ash Sawfly Read the factsheet

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