Join the RHS today and support our charitable work
Keep track of your plants with reminders & care tips – all to help you grow successfully
RHS members get reduced ticket prices
RHS members get free access to RHS Gardens
Free entry to RHS members at selected times »
Reduced prices on RHS Garden courses and workshops
020 3176 5800
Mon – Fri | 9am – 5pm
Help us achieve our goals
Join the RHS today and support our charity
The caterpillar-like larvae of two species of sawfly can occasionally cause considerable defoliation of pine trees.
Pine sawfly larvae
Adult pine sawflies (Diprion pini) are 10mm long brown winged insects, although they can appear fly like sawflies 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 25mm long and are pale green in colour with a brown head and black markings.
Fox-coloured sawfly (Neodiprion sertifer) larvae also reach 25mm in length are a dirty green colour with a black lateral stripe and a black head.
Both species feed in groups on the needles of pines during the spring and summer.
Heavy infestations of larvae can cause considerable defoliation of trees, whilst this is unusual in gardens when it occurs it can affect the growth of the trees.
Control is only feasible on trees that are small enough to treat, on large trees infestations have to be tolerated.
Larvae that can be reached can be removed by hand.
Pesticides for gardeners (Adobe Acrobat pdf document outlining pesticides available to gardeners)
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 spring brown cocoons on the foliage or on the ground beneath the plant. New adults emerging in July or August can produce a second generation of larvae that feed in late summer and autumn. The autumn generation spins a 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.
Chemical labels explained
Chemicals: using a sprayer
Chemicals: using safely and effectively
Large rose sawfly
Pear and cherry slugworm
Rose leaf-rolling sawfly
Social pear sawfly
Solomon’s seal sawfly
Willow leaf beetles
the RHS today and get 12 months for the price of 9
RHS members can get exclusive individual advice from the RHS Gardening Advice team.
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.