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Sawfly outbreak cause of willow death

Monday 11 February, 2008
The Goulburn Broken Catchment Management Authority (GB CMA) has reported an outbreak of willow sawfly* in the region.

The Goulburn Broken Catchment Management Authority (GB CMA) has reported an outbreak of willow sawfly* in the region.

The willow sawfly is an insect that feeds on willow trees** and large populations of the sawfly can actually kill the trees over time.

Willow trees are considered a weed of national significance they are highly invasive and have a negative impact on stream and terrestrial biodiversity. This is why the GB CMA are currently trying to manage willows within and adjacent to waterways by poisoning and removal, however, introducing the sawfly was not planned.

Mr Collin Tate a GBCMA Work's Supervisor in Seymour said the introduction of the willow sawfly was unexpected. We do have a plan in place to ensure that native vegetation is established soon after the removal or loss of any dead willows.

"The sawflies are targeting all willows except pussy willows and landholders should know that they are moving rapidly along streams in the area."

"The first outbreak in this region was noticed in November 2007 near the Hume Freeway at Seymour so there is a possibility the sawfly has hitched a ride to the area on a vehicle."

"It is now also attacking willows on the Goulburn River between Alexandra and Thornton and moving upstream to the Rubicon River. It has also been discovered in the wetlands in the Yea Township and has now reached creeks outside of Yea," said Mr Tate.

In 1999, willows were listed as one of Australia's 20 Weeds of National Significance because they choke rivers, change the natural flow of water, stop other native plants from growing and destroy river habitat.

If you would like to know how to stop the sawfly from destroying your ornamental garden willows then go to http://www.extension.umn.edu/distribution/horticulture/DG6703.html

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For more information please contact Stacey Brauman at Impress Publicity on 0400 644 637

*Willow sawfly is an insect which has recently arrived in Australia. Willow sawfly is native to much of the northern hemisphere. It was first recorded in South America in 1980, then in southern Africa in 1993 and New Zealand in 1997. It is unclear how willow sawfly arrived in Australia, but it was not introduced deliberately. It is possible that adult sawflies were blown across from New Zealand or that cocoons were accidentally imported, for example on shipping containers. Willow sawfly was first reported in Canberra in 2004 and, by April 2006, it had arrived in the ACT, NSW, South Australia, Victoria and Tasmania. Willow sawfly adults can fly 50-60 km, and the insects can also hitch a lift with human couriers. On a large scale, it is not possible to protect willow trees from willow sawfly with insecticide sprays. It may be possible to protect individual trees. Willow trees can die after 2-3 years of repeated defoliation events.

**Willows infest thousands of kilometres of waterways across southeast Australia and cause substantial social, economic and environmental impacts, including: increased erosion and flooding and damage to nearby infrastructure, reduced quality and flow of water, less habitat available for fish, birds, insects and spiders and reduced access to streams for fishing and aquatic activities. It is now illegal to trade or distribute most types of willows in all States and Territories and the control of certain willows is legally required in some areas. Willows have the potential to invade waterways, drainage lines, wetlands and other moist areas in all states and territories.