|Quarterly Update:||January March 2004|
|Final Report:||Final Report [PDF 1.5M]|
|Updated:||01 Feb 2008|
Defoliation caused by the recently invasive willow sawfly can have a devastating impact on willows planted to protect riverbanks and erodible hill country soils. Willow sawfly is a northern hemisphere pest that was first discovered in Auckland in 1997, and since then it has spread to most parts of the country. The sawfly larvae are external leaf feeders, and short generation times from egg to adult result in outbreaks that strip willows of leaves in mid summer, given suitable conditions. The Hawkes Bay, Gisborne, Waikato and Bay of Plenty have been the worst affected regions to date, with many reports of both young and mature trees dying. Even moderate damage to willows has forced changes in tree management practises by river engineers, and in the Hawkes Bay in September 2003 there were reports of worsening flood damage caused by small-moderate flood events. The damage caused to willows in affected regions has serious implications for the agricultural sector.
Three years ago a large willow sawfly research programme was initiated at HortResearch with the support of the Regional Councils. This programme researches the impact of sawfly, the sawfly lifecycle, and potential remedies (such as resistant willows, alternative species and biological controls). This SFF project is fulfilling a critical role in the dissemination of willow sawfly information and research updates to farmers and land owners. Two field days were held in Gisborne and Hawkes Bay on 6 March 2003 and 7 March 2003 respectively. John Charles and Lindsay Fung (HortResearch) were the main speakers. Three more workshops will be held in March 2004. A presentation was also made to the New Zealand Farm Forestry Association National Conference on 7 April 2003, as part of a field day attended by over 100 people. Handout material was distributed and the presentation was noted in the May 2003 issue of "The Tree Grower". A lengthy article has been prepared for publication in "Country Wide", and numerous articles about willow sawfly have appeared in regional newspapers. A project website has been developed at: http://www.hortresearch.co.nz/projects/sawfly/
The contact people for this project are Sarah Hurst (email: firstname.lastname@example.org or Ph. 06 356 8080 ext. 7840) and Alec Olsen (email: email@example.com).
Other key project members are: Alec Olsen and James Hunter (Hawkes Bay Farm Forestry Association the Applicant Group), Nick Seymour (Gisborne Farm Forestry Association), Stan Braaksma (Wellington Regional Council), Tony Dunlop (Environment Bay of Plenty), Ian McIvor (HortResearch), John Charles (HortResearch).
Photo 1: Sawfly larvae
Photo 2: Defoliated willows along Waipaoa River, Gisborne, in January
Defoliation caused by the recently invasive willow sawfly can have a devastating impact on willows planted to protect riverbanks and erodible hill country soils. Willow sawfly is a northern hemisphere pest that was first discovered in Auckland in 1997, and since then it has spread to most parts of the country.
A project website was developed in the September-December quarter. In November a questionnaire was sent to all Regional Councils to determine the history of sawfly in their region, and more specifically, which locations were affected in the 2002-03 summer. Information gathered from this questionnaire was used to develop a "Distribution" section in the sawfly website, which informs farmers and Regional Councils of willow sawfly outbreaks and the progression of sawfly throughout New Zealand. The website is now proving useful in sharing sawfly observations and knowledge between regions. A "Frequently Asked Questions" Section has also been developed, which is specifically designed for farmers and landowners who may be affected by sawfly. The website is now operational at the following address: http://www.hortresearch.co.nz/projects/sawfly/
Recent flood damage in the Manawatu-Wanganui region has highlighted the importance of riverbank protection and soil conservation plantings to prevent soil erosion. Defoliation caused by the recently invasive willow sawfly has had a devastating impact on willows planted to protect riverbanks and erodible hill country soils in many East Coast regions. If the flooding had occurred on a similar scale in Hawkes Bay we would expect to see more severe damage to protection works, due to the weakened state of the willows.
In the January- March quarter, Ian McIvor and Sarah Hurst (HortResearch) spoke about willow sawfly at three field days, in Gisborne, Wairarapa and Palmerston. There was a lot of interest in these presentations, particularly in Gisborne where farmers had experienced willow sawfly. The first willow sawfly brochure in a series of three was released in March. The brochures will be sent to Regional Councils nationwide, for distribution to interested farmers, landowners and general public.