Pine sawflies
The caterpillar-like larvae of two species of sawfly can in gardens, occasionally cause defoliation of pine (Pinus) trees.
Quick facts
Scientific names Diprion pini and Neodiprion sertifer
Plants affected Pine (Pinus)
Main symptoms Caterpillar-like larvae defoliate plants
Most active Spring-Summer
What are pine sawflies?
Sawflies are a group of insects in the suborder (Symphyta) of the Hymenoptera (bees, ants and wasps). There are about 500 species of
Adult pine sawfly (Diprion pini) are 10 mm long brown winged insects, The 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) is 7-9 mm long and pale orange-brown. The larvae reach 25 mm in length are a dirty green colour with a black
The larvae of both species of sawfly feed in groups on the needles of pines during the spring and summer.
Symptoms
Management
Sawflies can be a part the biodiversity a heathy garden supports
- Where possible tolerate populations of sawfly
- Encourage predators and other natural enemies of sawfly in the garden, such as birds and ground beetles
- Check plants regularly from spring for the presence of larvae and remove by hand where practical
Biology
Pine sawfly adults are active in spring and the females lay eggs in slits they make with an egg laying organ (ovipositer) in the needles. The larvae hatch after a few weeks and feed in groups on the needles. These larvae will lift their abdomen off the plant in a group as a defensive posture when disturbed. The larvae are usually fully grown by July where they spin brown cocoons on the foliage or on the ground beneath the plant. New adults emerging in July or August and can produce a second generation of larvae that feed in late summer and autumn. The autumn generation spins cocoons in soil or leaf litter, pupating in the following spring.
Fox-coloured sawfly adults are active in late summer and early autumn and lay eggs on the needles. The eggs overwinter and hatch in spring. The larvae feed in groups which will raise their abdomens when disturbed. In late June the fully grown larvae drop to the soil to pupate in an oval cocoon. This species has one generation a year.
See also...
BIg Garden Sawfly Survey
The sawflies of Britain and Ireland information on Fox coloured sawfly
The sawflies of Britain and Ireland information on Pine sawfly
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