The caterpillar-like larvae of two species of sawfly (pine sawfly and fox-coloured sawfly) they can on occasion cause serious defoliation of pine trees. They are at their most active in spring and summer. Pine sawfly is considered a pest as it eats a lot of needles; this can stunt the growth of the tree, it rarely is enough to kill the tree.

Adult pine sawflies (Diprion pini) are 10 mm long brown winged insects, although they can appear fly like, they are more closely related to bees, ants and wasps. The larvae of sawflies are similar in appearance to caterpillars. Pine sawfly larvae reach up to 25 mm long and are pale green in colour with a brown head and black markings.

Fox-coloured sawfly (Neodiprion sertifer) European sawfly larvae also reach 25 mm in length are a dirty green colour with a black lateral stripe and a black head. The European pine sawfly typically hatches from early April to late May. The larvae feed on existing pine needles.

Both species feed in groups on the needles of pines during the spring and summer.

Control is only feasible on bonsai trees as they are small enough to treat; on large trees infestations have to be tolerated. The larvae must be removed by hand.

Pesticide control:

If infestations are too heavy for hand picking, control may be achieved by spraying with pesticides. Spaying at dusk is likely to produce the best results.

Pine sawfly

Fox coloured sawfly

Sawfly larvae