Potential beneficial and adverse effects to be addressed in the EPA application to introduce the white admiral butterfly, Limenitis glorifica, as a biological control agent for Japanese honeysuckle
Richard Hill, Richard Hill & Associates, Richard.hill@plantandfood.co.nz, 03 3256400, 021 1376919
The potential beneficial and adverse effects of new control agents for a range of weeds have been identified systematically over a range of projects in the last ten years through formal brainstorming and through consultation with the public and professionals. This process has shown there is a suite of possible risks, costs and benefits that are common to all weed biocontrol proposals. Other effects are specific to particular agents (in this case for example, the relationship with the monarch butterfly adds an extra dimension). Effects can result from
- The introduction of a new element into the New Zealand environment
- The reduction in density and abundance of the weed through biological control
Here is the list of effects identified. Those potential risks or benefits considered to be significant (the product of the magnitude of the effect times the frequency or likelihood of the effect) have been highlighted, and will be addressed fully in the application. Those not considered to be significant (because they are speculative, or because the magnitude and/or likelihood of the effect is low) will probably not be addressed.
Please contact Richard Hill before 30 January 2013 if you have any comments about the approach to be used in the application, or to report additional potential effects.
Potential impacts on Māori values are addressed in a separate request for consultation.
Potential Beneficial Effects
On the Environment
- Defoliation by white admiral larvae reduces the biomass of Japanese honeysuckle and limits shading effects on underlying canopy vegetation and seedling establishment in forest margins
- Defoliation by larvae reduces fruit production and limits Japanese honeysuckle density in existing sites
- Defoliation by larvae reduces fruit production and the rate of spread of Japanese honeysuckle to new sites
- Reduction in abundance of Japanese honeysuckle reduces habitat for possums, which eat fruits
- Reduced incidence of Japanese honeysuckle partially restores natural vegetation, trophic webs and ecosystems
- Increased nutrient turnover in the litter beneficially affects natural nutrient cycles
- Increased/decreased nutrient flows in weed patches beneficially affects regeneration
- Reduction in abundance of Japanese honeysuckle reduces habitat for pest insects such as passion vine hopper and leafrollers
- Introduction of new species increases biodiversity
- Successful control leads to resumption of regeneration in some affected forest margins and other sensitive habitats
- Reduced competition with native seedlings including native vines
- Reduced damage to underlying foliage from spraying
- Improved access to underlying resources for birds
- Benefits to parasitoid, predator and disease relationships in trophic webs
- Increased nutrient turnover in the soil beneficially affects natural nutrient cycles, increasing the growth rate and survival of valued forest seedlings.
- Reduced contamination of air, soil and water from reduced spraying
- Improved look and feel of native bush for visitors
- Increased C accumulation in affected/shaded trees
- Loss of endangered species slowed.
- New Zealand's biodiversity is increased
- Successful control leads to improved invertebrate biodiversity in bush margins
- Increased nutrient turnover in the litter beneficially affects natural nutrient cycles
On Human Health
- Reduction in muscular strains to gardeners, conservation staff and volunteers caused by physical removal of Japanese honeysuckle
- Improved health from reduced occupational exposure of gardeners, conservation staff and volunteers to herbicides
On the Market economy
- Successful biological control leads to reduction in the cost of control for occupiers, regional councils, DOC, and others
- Reduced control costs/increased production in production forests
- Costs of controlling replacement weeds is lower than Japanese honeysuckle
- Management of control agents creates business opportunities for Landcare Research
On Society and Communities
- Replacement of Japanese honeysuckle with native vegetation following successful biological control leads to improved conservation values
- Successful biological control leads to better use of conservation volunteers and community resources
- Successful control leads to less Japanese honeysuckle management by home gardeners
- Successful control leads to fewer new invasion sites through less dumping of Japanese honeysuckle in garden waste
- Landscape values improved by decline in Japanese honeysuckle ground cover
- Reduction in stress in conservation workers
- Reduced abundance of Japanese honeysuckle reduces nuisance value to householders (including safe disposal, damage to clothes, skin irritation), reducing time allocated to control, and reducing non-target damage from backyard herbicide application.
Potential Adverse Effects
On the Environment
- Feeding by white admiral larvae reduces native plant populations
- Japanese Honeysuckle abundance declines leading to invasion by worse weeds
- Defoliation reduces fruit production of Japanese honeysuckle, and the food supply for native fruit-feeding birds
- Introduction of the white admiral to native habitats adversely affects native parasitoid, predator and disease relationships
- Food web interactions are adversely affected by the introduction of new prey species. Indirect competition causes extinction of native insects
- Control agents hybridise with related resident insects
- Swift evolutionary change in insect leads to unexpected non-target damage to valued plants and/or alterations to food webs
- Selecting agent populations other than those tested leads to unpredicted non-target effects
- Larval feeding on leaves reduces susceptibility of Japanese honeysuckle to herbicides, and application rates increase
- Successful control reduces habitat quality for native fauna
- Larval feeding changes nutrient flows in weed patches adversely affecting regeneration
- Massive frass production and heavy destruction of plant material over a short time reduces quality of bordering streams
- Successful control leads to reduced invertebrate biodiversity in bush margins
On Human Health
- Butterflies cause nuisance indoors
- Public fearful of insects
- Loss of useful future phytomedicines from control
- Butterflies bite or sting
- Butterflies generate allergic response
- Butterflies need spraying with adverse effects to humans
On the Market economy
- Feeding by white admiral larvae significantly reduces the usefulness of honeysuckle-like plants making sale in nurseries unprofitable
- Successful biological control leads to reduced herbicide sales significantly affecting vendors’ businesses
- Feeding on larvae increases wasp populations and hence wasp control costs
- Adverse effects require costly agent eradication campaign
- Successful biological control reduces revenue for contractors and suppliers
On Society and Communities
- Significantly increased incidence of wasp stings by wasp populations increased by eating larvae
- Fear and distrust of exotic species and their possible non-target effects.