Summary of Staff Assessment Report APP203853: An application to - - PowerPoint PPT Presentation

Summary of Staff Assessment Report

APP203853: An application to release the parasitic wasp Pauesia nigrovaria as a biological control agent for the giant willow aphid

24 October 2019

The application 2

• Scion lodged an application with the Environmental Protection

Authority on 24 July 2019 to release the parasitic wasp, Pauesia nigrovaria as a biological control agent for the giant willow aphid, Tuberolachnus salignus.

• The application was publicly notified. The EPA received 50

submissions with 45 in support, three neither in support nor

• pposing and two in opposition.
• Seven submitters indicated they wish to be heard.

Target pest – giant willow aphid (GWA)

• East Asia
• Up to 5.8mm long, reproduce asexually, no males

known, winged and non-winged individuals

• Can produce four offspring per day at 20°C
• Can remain active in frost and heavy snow and

may remain on host trees long after they have shed their leaves

• Primarily a pest of willow trees but can also affect

apple, pear and coastal karamu

• No specialised predator for GWA

3

Adult giant willow aphid. Alex McCarthy, 2016.

Effects of the GWA in New Zealand

• Impacts willow tree health and can cause mortality
• Increases riverbank instability
• Produces honeydew
• Junk food for honeybees and an additional food source for pest wasps
• Honeydew excreted and covers substrate in close proximity
• Sooty mould develops on honeydew
• Reduces photosynthetic ability of plants
• Economic impacts for apiculture, horticulture and wool industries

4

Distribution of GWA in New Zealand

• Discovered in Auckland, December

2013

• Within one year had an almost

cosmopolitan distribution

• Found in rural and urban environments
• Colonies have been observed on all

known willow varieties in the North Island

5

Proposed biocontrol agent: Pauesia nigrovaria

• ≈ 3mm long
• Does not sting humans and is non-toxic
• Endoparasitoid
• Attacks GWA in both Asia and California, USA
• Pauesia genus highly specialised – 39 of 75

Pauesia spp. parasitise only one species of aphid

• Pauesia use different chemical stimuli to

locate hosts

6

Adult female P. nigrovaria wasp. Stephanie Sopow, Scion.

Risk/benefits assessment 7

• We assessed the risks and benefits of releasing this organism in

New Zealand, assuming the successful establishment of self- sustaining populations.

• We assessed the risks and benefits to:
• the environment,
• market economy,
• people and communities,
• Māori and their relationship with the environment, and
• public health.

Environmental benefits 8

• Reduction in GWA abundance
• Improved health of willow tree species
• Increased availability of willow pollen and nectar in spring
• Improved environmental conditions for honeybees in spring
• Reduced production of honeydew
• Improved biodiversity and conservational values
• Reduced chemical pesticide usage

The magnitude of effects are variable depending on the impact of P. nigrovaria. While benefits are highly likely or likely to occur, we estimated the environmental benefits to be medium to low.

Economic benefits 9

• Reduced formation of unmarketable cement honey
• Reduced destruction of beehives by pest wasps
• Reduced abundance of sooty mould development on economically

significant horticultural and wool industries We concluded that benefits to the market economy would be highly likely to likely and determined the magnitude of benefits to be moderate to minor.

Environmental risks 10

• Non-target impacts on native aphid species
• Hybridisation with native wasp species
• Altering food web interactions to cause displacement of native organisms
• Cause indirect effects to other organisms through reduced GWA abundance
• Pauesia nigrovaria is unpalatable to predators and increases nectar

competition

• Improved pest willow health and environmental conditions for these spp.

We concluded there would be negligible/low indirect adverse effects and the magnitude of the effects to be minimal/minor.

Economic risks 11

• No economic risks associated with releasing P. nigrovaria identified

What are the risks of not releasing P. nigrovaria? Increased abundance of GWA across New Zealand which leads to…

• greater honeydew produced
• greater production of cement honey, more sooty mould
• greater losses in the apiculture industry and potentially loss of market

access, greater losses in horticultural and wool industries

Summary of our assessment - Benefits 12

Keys areas Likelihood / Magnitude Conclusion (level of benefit)

Benefits

Environment

• Reduce GWA abundance
• Reduce GWA impact on willow health
• Improve soil stability of river banks
• Improve biodiversity values

Highly likely / Moderate Highly likely / Moderate Likely / Minor Likely / Minor Medium Medium Low Low

Economy

• Reduced formation of cement honey
• Reduction of sooty mould
• Benefits to wool industry

Highly likely / Moderate Likely / Moderate Likely / Minor Medium Medium Low

Summary of our assessment - Risks 13

Keys areas Likelihood / magnitude Conclusion (level of risk)

Risks Risks

Environment

• Attack on native aphid species
• Effects on food webs and ecosystems
• Improve pest willow tree health
• Hybridisation with other wasp spp.

Highly improbable / Minimal Unlikely / Minimal Likely / Minor Highly improbable / Minimal Negligible Negligible Low Negligible

There are no direct economic risks associated with the release of P. nigrovaria as any potential establishment of self-sustaining populations will not be considered as undesirable.

Relationship of Māori to the Environment 14

• Kaupapa Kura Taiao completed a cultural risk assessment of the application and concluded the

potential benefits of releasing P. nigrovaria are likely to outweigh the risks/costs.

• The potential risks to Māori interests would probably be acceptable.
• “The benefits to Māori associated with this application are likely to outweigh any detrimental

impacts to Māori. The overall impact on the relationship Māori have with their environment and taonga is likely to be enhanced, depending on the efficacy of the parasitoid wasp.”

Minimum standards

• We assessed the release of P. nigrovaria against the minimum standards (s36) in the HSNO Act.
• We concluded that P. nigrovaria meets the minimum standards.

Recommendation 15

• We found the benefits of releasing P. nigrovaria outweigh the

risks and costs.

• We determined P. nigrovaria meets the minimum standards.
• We recommend the decision-making committee approve the

release of P. nigrovaria.

For more information contact:

General enquiries Phone +64 4 916 2426 Fax +64 4 914 0433 info@epa.govt.nz