Potential beneficial and adverse effects to be addressed in the EPA application to introduce two agents, a moth, Lathronympha strigana, and a leaf beetle, Chrysolina abchasica, as biological control agents for tutsan
The potential beneficial and adverse effects of new control agents for a range of terrestrial weeds have been identified systematically over 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 most weed biocontrol proposals. Other effects are specific to particular agents. 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 and 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 or cannot be clearly demonstrated) will probably not be addressed.
Please contact Richard Hill, preferably before 30 September 2015 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 consultation process
Potential Beneficial Effects
On the Environment
- Attack on leaves and stems reduces the biomass or abundance of tutsan and limits shading effects, reversing plant diversity loss in native forest gaps and margins.
- Leaf damage or direct attack reduces fruit production and limits rise in tutsan density in existing sites
- Leaf damage or direct attack reduces fruit production and limits dispersal by birds to new sites
- Reduced incidence of tutsan 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 tutsan reduces habitat for pest insects
- Introduction of new insect species increases biodiversity
- Reduced competition with native seedlings
- Reduced collateral damage to native plant species from spraying
- Improved access to native 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
- Loss of endangered species slowed.
- New Zealand's biodiversity is increased
- Successful control leads to improved invertebrate biodiversity in bush margins
On Human Health
- Reduced abundance reduces the incidence of tutsan related poisoning
- Reduction in muscular strains to gardeners, conservation staff and volunteers caused by physical removal of tutsan
- Improved health from reduced occupational exposure to herbicides of gardeners, conservation staff and volunteers
On the Market economy
- Successful biological control leads to reduced control costs/increased production in pastoral agriculture
- Successful biological control leads to reduction in the cost of control for occupiers, regional councils, DOC, infrastructure companies and others
- Successful biological control leads to reduced control costs/increased production in production forests
- Costs of controlling replacement weeds is lower than tutsan
- Management of control agents creates business opportunities for Landcare Research
On Society and Communities
- Replacement of tutsan 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
- Landscape values improved by decline in tutsan density
- Reduction in stress in conservation workers
Potential Adverse Effects
On the Environment
- Feeding damage by control agents reduces native plant populations
- Decline in tutsan abundance leads to invasion by worse weeds
- Defoliation reduces fruit production of tutsan, and the food supply for native fruit-feeding birds
- Introduction of the insects to native habitats adversely affects native parasitoid, predator and disease relationships
- Food web interactions are adversely affected by the introduction of a new prey species. Indirect competition causes extinction of native insects
- Control agents hybridise with related resident insects
- Swift evolutionary change in insects 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
- Feeding on leaves reduces susceptibility of tutsan to herbicides, and application rates increase
- Successful control reduces habitat quality for native fauna
- Insect feeding changes nutrient flows in weed patches adversely affecting regeneration
- Massive leaf-fall over a short time reduces quality of bordering streams
- Successful control leads to reduced invertebrate biodiversity in bush margins
On Human Health
- Control causes loss of future phytomedicines
- Insects cause a nuisance indoors
- Public fearful of insects
- Control agents bite or sting
- Control agents generate allergic response
- Control agents need spraying with adverse effects to humans
On the Market economy
- Damage on leaves significantly reduces the usefulness of valued ornamental species, making sale in nurseries unprofitable
- Successful biological control leads to reduced herbicide sales significantly affecting vendors’ businesses
- Feeding on agents 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
- Damage, and/or reduction in flowering reduces the ornamental value of Hypericum bushes currently growing
- Significantly increased incidence of wasp stings by wasp populations increased by eating agents
- Fear and distrust of exotic species and their possible non-target effects.