Biological Control Flashcards
What is biological control?
Use of predators, parasitoids and pathogens to regulate pest densities
Long history of use in pest management
Focus of renewed attention
- Food security worldwide
- EU policy on pesticides
- Pest resistance and pollution
- Green technology
- Uncertainty over GM crops
Types of biological control
- Classical: Control of alien species using small scale releases leading to permanent establishment of co-evolved natural enemies from origin of pest
- Inundative: Mass release of laboratory-reared populations (indigenous or non- native) to control open field or glasshouse pests - do not persist
- Conservation: Sustainable use of indigenous IBCAs against indigenous or non- native pests
Classical biological control
Rodolia cardinalis (Cardinal Ladybird) has been used for control of Iceryae purchasi (Cottony Cushion Scale) in California for over 100 years.
Both the adults and larvae of the Cardinal Ladybird actively predate Cottony Cushion Scale insects.
Inundative biological control
Mass release of parasitoids such as Encarsia formosa (a parasitic wasp) to control glasshouse whitefly Trialeurodes vaporariorum
Trichogramma species have been used in open-field control of maize corn borer Ostrinia nubilalis
Conservation Biological Control
Beetle banks provide refuges for many natural enemy species that declined with removal of hedgerows
Carabid beetles are polyphagous predators that require overwintering sites
Adults of some natural enemies have different food requirements to their immature stages, which are the ‘control’ agent
Hoverfly larvae predate aphids, but adults feed on flowers that can be planted in headlands
Limitations of Biological Control
Types of pests
Early successes against scale insects, but many taxa now controlled
Islands and continents
Successful on real or ecological islands, but also across continents
Climate
Most successes in tropical/Mediterranean climates – winter is a major limitation
Comparison of chemical and biocontrol
Invertebrate BCAs – historical context
Invertebrate biocontrol agents have been used in pest management for over 100 years
“More than 5000 introductions of about 2000 species of exotic arthropods for control of arthropod pests in 196 countries or islands during the past 120 years have rarely resulted in negative environmental effects.”
“Yet, risks of environmental effects caused by releases of exotics are of growing concern. Twenty countries have implemented regulations for release of biological control agents.”
What are the risks of biological control?
Human Health
Allergies – a few examples in production facilities, but rare
Nuisance pests – Harmonia axyridis in houses
What are the risks of biological control?
Crops and plants
Some biocontrol agents also feed on plants e.g. Macrolophus caliginosus on tomato
Some biocontrol agents contaminate crops e.g. Harmonia axyridis in grapes
What are the risks of biological control?
Environment
Non-native species may establish in new country
Introduced species may attack non-target species
May displace native insects important in natural control and other ‘exotics’ used in biological control
May carry hyperparasites or pathogens
May disrupt ecosystem functions – pollination
May interbreed with native species
Regulation of Invertebrate BCAs in Europe
In countries with regulation, no consistency in information required for risk assessment
Reliance on published literature – information often unavailable
Assumptions made on basis of ‘climate matching’ as a proxy for direct assessment of thermal tolerance – tropical species will not establish in temperate and colder climates
Approach has allowed release and establishment of non-native insects and mites
ERA for invertebrate BCAs
Environmental Risk Assessment should be:
- Quantifiable - environmental effects of different biological control agents can be compared and choices made
- Hierarchical - a tiered or step-wise procedure
- Provide quick identification of safe or hazardous agents with minimum costs
Generic hierarchical ERA
Distinguishes between Exotic/Native, and Augmentative/Classical control
Has ‘Full’ and ‘Quick’ Scan options
Identifies key features of ERA:
Establishment
Host range
Dispersal
Direct effects
Indirect effects
ERA methods: Host range
Macrolophus caliginosus is a polyphagous predator targeted against Glasshouse Whitefly (Trialeurodes vaporariorum)
If its host range was NOT known, could test performance on glasshouse target, a close relative (Cabbage Whitefly Aleyrodes proletella) and a common ‘unrelated’ species e.g. aphid Myzus persicae
Compare development and reproduction
