Potential beneficial and adverse effects
Leptophya hospita male (L) and female (R).
Effects to be addressed in the EPA application to introduce the privet lace bug, Leptoypha hospita, as a biological control agent for privet species
Richard Hill, Richard Hill & Associates, hillr@landcareresearch.co.nz, 021 765813
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. 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 in bold, 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 19 September 2014 if you have any comments about the approach to be used in the application, or to report additional potential effects.
Potential impacts on Maori values are addressed in a separate consultation process.
Potential Beneficial Effects
On the Environment
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Defoliation by privet lace bug reduces the biomass or abundance of privet in forest and stream margins, bush remnants and forest understory and reduces competition with native seedlings, leading to improved biodiversity of native flora and fauna
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Defoliation reduces fruit production and limits privet density in existing sites
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Defoliation reduces fruit production and the rate of spread of privet to new sites
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Reduced incidence of privet 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
- Introduction of new species increases biodiversity
- Successful control leads to resumption of regeneration of native plants in some affected forest margins and other sensitive habitats
- Reduced damage to underlying foliage from spraying
- 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
- 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
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Reduction in biomass of privet reduces flower production and the exacerbation of allergic reactions
- Reduction in muscular strains to gardeners, conservation staff and volunteers caused by physical removal of Privet
- Improved health from reduced occupational exposure of gardeners, conservation staff and volunteers to herbicides
On the Market economy
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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 Privet
- Management of control agents creates business opportunities for Landcare Research
On Society and Communities
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Replacement of Privet with native vegetation following successful biological control leads to improved conservation values
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Successful biological control leads to better use of conservation volunteers and community resources
- Improved look and feel of native bush for visitors
- Successful control leads to less Privet management by occupiers
- Successful control leads to fewer new invasion sites through less dumping of Privet in garden waste
- Landscape values improved by decline in Privet invasion of hedgerows and other places
- Reduction in stress in conservation workers
- Reduced abundance of Privet 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
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Feeding by Privet lace bug reduces native plant populations
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Privet abundance declines leading to invasion by worse weeds
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Defoliation reduces fruit production of Privet, and the food supply for native fruit-feeding birds
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Introduction of the Privet lace bug to native habitats adversely affects native parasitoid, predator and disease relationships
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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 Privet 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
- Insects cause nuisance indoors
- Public fearful of insects
- Loss of useful future phytomedicines from control
- Insects bite or sting
- Insects generate allergic response
- Insects need spraying with adverse effects to humans
On the Market economy
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Feeding by Privet lace bug significantly reduces the usefulness of lilacs, making sale in nurseries unprofitable
- Successful biological control leads to reduced herbicide sales significantly affecting vendors’ businesses
- Adverse effects require costly agent eradication campaign
- Successful biological control reduces revenue for contractors and suppliers
On Society and Communities
- Fear and distrust of exotic species and their possible non-target effects.