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The greyish-brown caterpillar like larval stage of iris sawfly can completely defoliate flag iris and other waterside iris in summer.
Iris sawfly (Rhadinoceraea micans) on yellow flag iris (Iris pseudacorus)
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.
Iris sawfly has greyish-brown larva that reach 25 mm in length and eat the foliage of flag iris (Iris pseudacorus) and other waterside irises, including Iris spuria, I. versicolor, I. laevigata and I. ensata. The adults are similar in appearance to some other species of sawfly and have black heads and bodies up to 8mm long with smoky grey wings.
Iris sawfly larvae can feed in groups so damage can occur very quickly and defoliation can be extensive. Keep vigilant for early signs;
Regularly inspect plants during the growing season and where possible remove larvae from the leaves.
Insecticides cannot be used against this insect because of the danger to fish, frogs, toads and other aquatic life in water bodies where irises grow.
Iris sawfly adults are active in late April-May and soon lay eggs on the foliage of host plants. The greyish-brown caterpillar like larvae, speckled with small white spots and up to 25mm long, are present in June-July. The larvae initially eat V-shaped notches from the leaf margins but later devour the foliage from the leaf tips downwards.
There is one generation a year and larvae overwinter in the soil before pupating in the following spring.
Rose large sawfly
Rose leaf-rolling sawfly
Solomon’s seal sawfly
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