Willow sawfly (Nematus oligospilus)
What is it?
Willow sawfl y is an insect which has recently arrived in Australia. The larval stage of the life cycle feeds on willow leaves, and large populations of larvae can defoliate adult willow trees.
Where did it come from?
Willow sawfl y is native to much of the northern hemisphere. It was fi rst recorded in South America in 1980, then in southern Africa in 1993 and New Zealand in 1997.
How did it get here?
It is unclear how willow sawfl y arrived in Australia, but it was not introduced deliberately. It is possible that adult sawfl ies were blown across from New Zealand or that cocoons were accidentally imported, for example on shipping containers. ... Read the PDF Flyer here
Where is it now?
Willow sawfl y was fi rst reported in Canberra in 2004 and, by April 2006, it had arrived in the ACT, NSW, South Australia, Victoria and Tasmania. Willow sawfl y adults can fl y 50-60 km, and the insects can also hitch a lift with human couriers, so it is expected that willow sawfl y will soon spread to all suitable areas.
What conditions suit willow sawfl y?
Rapid population increases seem to be associated with warm, dry spring conditions. It is not known if high temperatures affect survival and reproduction of willow sawfl y. In ideal conditions, willow sawfl y can develop from an egg through its life cycle to an adult within four weeks. Several generations can develop each season, from about October to April.
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