Unintentional biological control.
Recent frequent and surprisingly rapid accidental natural enemy introductions call into question the regulatory emphasis on a rigorous and protracted process for approving importation biological control introductions, when adventives (unintended introductions, not infrequently the same species of natural enemies under evaluation) have a high probability of displacing or disrupting this planned process. Several major invasive pests have been associated with accidental introductions of their natural enemies, with varying outcomes, some still unclear. Introductions of still other natural enemies, some trophic generalists, are not associated with any particular pest. This chapter provides a brief overview of several examples, including parasitoids and pathogens of arthropod pests, and weed biological control by an herbivorous insect.