GWA Media Release                                                                                                                                  

Giant Willow Aphid collaborative research wins funds

A major collaborative project to reduce the impacts of the Giant Willow Aphid has been awarded $425,629 funding by MPI’s Sustainable Farming Fund towards a research project worth close to $600,000 including in kind contributions.

Apiculture New Zealand, together with Scion, Plant and Food Research, and a number of other key partners including MPI, will begin research immediately on a range of initiatives to reduce the impacts of the aphid.

“We are delighted that our application has been successful,” says Barry Foster, Chair of the Research Focus Group of Apiculture New Zealand. “The aphid is already causing serious problems for beekeepers but we are definitely not the only people affected. A coordinated approach is by far the best way to get both short- and long-term control measures in place as quickly as possible.”

Justine Gilliland, Investment Programmes Director for the Ministry for Primary Industries, was pleased to be able to support the project through the Sustainable Farming Fund (SFF).

“Initially we were unable to support this project in the last funding round, but funds have come available due to underspend in other SFF projects. We are aware of the negative affect the Giant Willow Aphid is having on primary industries such as the apiculture industry.

“Through the Sustainable Farming Fund, MPI invests in projects that look into a shared problem or opportunity and our independent panel felt this project fitted well within our criteria. We look forward to seeing the positive outcomes the project generates over the next three years.”

The Giant Willow Aphid (Tuberolachnus salignus)was first discovered in New Zealand in 2013, and has a cascading detrimental effect on several industries. The aphid attacks and severely damages willow trees, reducing vigour and may eventually kill the trees.  The aphid creates a type of honeydew, attractive to bees, but which makes honey unusable, and has a number of other negative impacts across a range of sectors.

The three-year project will focus on three key research areas:

  1. Biological control: assessing the potential of a parasitic wasp biological control agent to suppress the aphid, and conducting detailed testing in containment in New Zealand (led by Scion)
  2. Host resistance: screening willow cultivars to identify resistant willow and poplar cultivars that can replace affected trees within the landscape (led by Plant and Food Research)
  3. Risk mitigation: investigating short-term risk-mitigation strategies based on hive management techniques (led by Apiculture New Zealand).

 “Biological control offers the best long-term solution for the aphid,”  says Scion entomologist, Stephanie Sopow. “We will work closely with overseas entomologists to assess the suitability of a known natural enemy. The process of approvals and testing – all the steps needed to safely introduce a new biological control agent and finally release it – take several years. The sooner we can make a start, the better.”

Current partners in the project

  • Apiculture New Zealand, Scion, Plant and Food Research, Poplar and Willow Research Trust
  • River Managers Group (regional councils), Trees for Bees, Wasp Tactical Group
  • Ministry for Primary Industries (MPI)

 Contacts for media

  1. Barry Foster, Chair, ApiNZ Research Focus Group
    06 867 4591; 027 449 7131
  1. Lindsay Bulman, Scion
    DDI: 07 343 5533
  1. MPI media phone
    029 894 0328

Further details on the impacts of the Giant Willow Aphid (GWA):

Giant Willow Aphid and the apiculture industry

  1. Decreased spring pollen and nectar supplies
    Willows and poplars are a critical source of pollen and nectar for bees in spring – this is a time when few other bee-friendly species are flowering. Heavy infestations of GWA on willows – for example in riparian plantings on farms – will reduce the vigour and flowering capacity of these trees, in turn reducing the feed supply for bees at a critical time in order to build hives up for pollination of crops and for honey production.
  2. Cement honey reduces honey harvest
    The honeydew secreted by GWA is rich in melezitose, a trisaccharide sugar. GWA honeydew is readily collected by bees. The honeydew is processed by bees into melezitose-enriched honey, which has a tainted flavour. This honey crystallises in the hive into a solidified or ‘cement’ honey which is difficult to process. As yet unquantified volumes of combs are now either sitting in warehouses, or being fed to livestock. Losses to beekeepers can be significant.
  3. Increased wasp numbers cause additional problems to beekeepers

The threat to willows in soil conservation and the rural landscape

Regional councils plant willows to assist with river management – their fibrous, fast-growing roots are the best biological tool available to help stabilise river banks. Many thousands of willows and poplars are also planted on hill country farms each year to reduce soil erosion. The rural New Zealand landscape is greatly enhanced by the spring and autumn colours of willows and poplars, and these trees are also popular in amenity areas like parks and gardens.

The GWA poses a significant threat to these trees: it colonises willow trees in great numbers, and is a voracious feeder. It also colonises poplars and other tree species. Young and old trees are likely to be particularly vulnerable to infestation, and dead willows may become a common feature in our landscape.

Honeydew –associated problems

Honeydew has a number of other unwanted and costly side-effects.

  • Wasps love honeydew – vespulid wasps are honeydew feeders, and where there are aphids there are generally many more wasps. Wasps are a health hazard and an extreme nuisance to people and animals.
  • Aphids produce so much honeydew that it literally ‘rains’ down on anything near to infested trees: cars or washing on the line in urban areas; livestock or near-by crops on farms. Farmers have reported that sheep rapidly become sticky and then covered in dust: dirty fleeces are difficult to process and the wool clip is down-graded.
  • Surfaces coated with honeydew soon develop sooty mould. This is unpleasant and unsightly: kiwi-fruit growers and other horticulturalists are encountering problems with sooty mould on their crops.