Regardless of the target pest, a similar series of steps are followed in any classical biological control project.
Species chosen as targets of importation biological control should be ones for which there is broad social agreement that they are pests and need to be reduced in density. Targets should be species that are strongly regulated by natural enemies in their native ranges and these species should be missing in the areas invaded by the pest. Nontarget risk to native plants can be minimized if species selected as targets do not have closely related (same genus) species in the recipient country.
Correct identification of the target pest is essential. Mistakes at this stage will cause project delays or failure. If the pest is an unknown species, its nearest relatives need to be identified, as this can provide clues to the pest's native range. Molecular markers are now commonly used to identify populations of both pests and natural enemies with increased precision. Such identification for pests allows exact origins of an invader population to be identified, often within very large native ranges. Markers for natural enemies allow biotypes or cryptic species to be recognized and facilitates identification of recovered specimens after release.
The region where the pest evolved needs to be identified as it is the best place in which to search for specialized natural enemies that have evolved with the pest. This can be done based on several criteria, including the center of the geographic range of the pest, the area where the principal host plant of the pest evolved, regions where the pest is recorded to occur, but remains at low densities, and regions with the largest numbers of species closely related to the pest.
Natural enemy collection, or foreign exploration, needs to be done extensively over the range of locations, habitats, and seasons where the pest is found naturally. Surveys of natural enemies in the invaded area are unlikely to locate effective natural enemies, but are needed to identify any natural enemies that may already be present because of their own invasion of the region.
Promising natural enemies collected in surveys need to be shipped to quarantine laboratories, where they can be colonized and maintained on the pest for further study to evaluate their host ranges and make a judgment as to their safety for introduction into the proposed recipient country.
To promote selection of safe species for importation, the biology and degree of host specificity of each candidate biological control agent needs to be determined through a mixture of literature records, field observations in the area of origin, and laboratory host range studies (feeding and oviposition evaluations with species potentially at risk) in quarantine before release into a new area is approved.
Releases need to be made at numerous locations where the target pest is present, and over extended periods of time until efficient means to establish the natural enemies in the invaded area are discovered or until it is clear the agents are unable to establish. Once established, natural enemies disperse naturally or are redistributed artificially throughout the range of the pest.
Field experiments in the invaded area comparing pest density in plots having and lacking the introduced natural enemy are needed to measure the degree to which the natural enemy is able to reduce the density of the pest (for insect targets) or, for weeds, how much the natural enemies lower a variety of plant performance and population measures such as percent cover, biomasss, seed set, etc.
Documentation of benefits
Economic and ecological consequences of the project need to be recorded and published.
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