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The caterpillar like larval stage of aruncus sawfly can defoliate goat's beard (Aruncus dioicus) in spring and summer.
Aruncus sawfly (Nematus spiraeae) on goatsbeard (Aruncus dioicus)
Sawflies are in the same group of insects as bees, ants and wasps (the Hymenoptera). They have caterpillar like larvae that feed on plants the adults are winged insects that can appear fly like.
Aruncus sawfly larvae feed in groups so defoliation can occur quickly. Keep vigilant for early signs from May onwards;
Damage can be expected from May (first generation), with a second generation in July and August and a third generation in September.
Regulary inspect plants during the growing season and remove larvae from the leaves.
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This sawfly defoliates goat's beard (Aruncus dioicus), a plant that was formerly included in the genus Spiraea, so this insect is sometimes known as the spiraea sawfly. It occurs in gardens throughout Britain wherever its host plant is grown.
The adult sawfly is 5-6mm long and has a black head and thorax with a yellow abdomen marked with dark bars on the dorsal surface. Larvae overwinter in the soil and, after pupation, adults emerge in May and lay eggs that hatch after about 7 days. Two or three generations of pale green larvae with brown heads feed gregariously on the foliage during the summer months, reducing the leaves to a network of the larger leaf veins. The pupal stage takes place within a silk cocoon in the soil.
This is a species that reproduces asexually and all the adults are female.
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Rose large sawfly
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Rose slug sawfly or slugworm
Social pear sawfly
Solomon’s seal sawfly
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