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July 2012



PSAUS defoliated by lesser willow sawfly (Nematus pavidus) larvae

It’s only the middle of July but the PSAUS, a willow (Salix) has already lost most of its leaves…

Nope, autumn hasn’t come early. It has been munched to destruction by these hungry fellas: lesser willow sawfly (Nematus pavidus) larvae.

I recognised them straightaway as sawfly larvae, rather than caterpillars, after the Set A grey alders played host a similar species a few years ago.

This photograph shows a birch sawfly aka hazel sawfly (Croesus septentrionalis) larva on grey alder No. 3 in October 2009...

…and on the same day I took this photograph of an alder sawfly (Eriocampa ovata) larva on grey alder No. 2.

Little wonder the PSAUS has been almost entirely defoliated – there are dozens and dozens of larvae! I’ve decided to leave them to do what they do best, and wait and see whether or not the PSAUS can weather the storm.

In this photo the second-right larva is caught in a classic pose while the furthest-right larva has an injury halfway along its body.


Posted in Pests and diseases + The treeblog trees












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