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Common Pine Sawfly

Diprion pini

Common Pine Sawfly , Pine Sawfly

A close up of a Pine sawfly Diprion pini against a white background
Male diprion pini by Sorneguer (CC BY-SA 3.0)
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Sawflies look a bit like large black flies. Don't be fooled; these flies are more closely related to bees, wasps and ants! A Common Pine Sawfly female lays her eggs in Pine (Pinus). This way, the larvae can begin to feast as soon as they've hatched from the egg. D. pini is a significant pest in forestry, but less of a problem in gardens. They're most damaging when a plant is already suffering from another pest, disease or disorder. By tending to your tree and ensuring good health, plants can recover in no time!
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Traits

Larvae can defoliate trees when in abundance.
Mature adults are pollinators in the garden.

Appearance

Adults: Adults are a chunky fly-like insect. The wings are folded neatly over each other and are held flat against the body. Females are light brown, with short antennae and plump abdomens. Males are much darker, almost black. They possess extensive fanned or feathered antennae, and these are used to detect a female's scent from far away! Larvae: Larvae start as tiny green worms, but after some growth look more like caterpillars. They're pale green and acquire black markings as they grow bigger. The heads are a light brown-orange.

Symptoms

Large infestations can defoliate trees. Severe infestations can stunt growth.

Activity

Diurnal

Personality

Order

Hymenoptera

Family

Diprionidae

Metamorphosis

Complete

Distribution

The UK and Europe

Biological treatment

Because these insects specifically target pine trees, sometimes treatments can be ineffective when the plants are too big. It's also thought that larger trees can tolerate infestations. If trees are small, you can pick off caterpillars and feed them to the birds! Attract natural garden predators into the garden by providing spots of cover. Wild patches and strips of native wildflower/ grass can provide cover for predatory insects. Climbing plants such as ivy is excellent habitat for small songbirds. Likewise, bird tables and ponds are an excellent resource for attracting wildlife.

Chemical treatment

If infestations are substantial, and trees reasonably sized, there are chemical alternatives. Plants intended for consumption should not be sprayed unless stated on the bottle label. Never apply to flowering plants. There are chemical alternatives available for home use, and these vary in the degree of persistence and strength. These include organic sprays (containing natural pyrethrums); winter washes (these contain natural plant oils and are particularly good for vines); and lastly, the more persistent chemicals (containing synthetic pyrethroids).

Attracts

Pine

Pinus spp.

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Plant Knowledge

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