Abstract:
Biological control is a valuable and effective strategy for controlling arthropod pests
and has been used extensively against invasive arthropods. As one approach for control of
invasives, exotic natural enemies from the native range of the pest are introduced to areas where
control is needed. Classical biological control began to be used in the late 1800s and its use
increased until, beginning in 1983, scientists began raising significant concerns and questions
about nontarget and indirect effects that can be caused by these introductions. In recent years,
similar issues have been raised about augmentative use of exotic natural enemies. Subsequently,
international guidelines, national regulations and scientific methods being used for exotic natural
enemies in biological control have changed to require appropriate specificity testing, risk
assessment and regulatory oversight before exotic natural enemies can be released. National and
international standards aimed at minimizing risk have increased awareness and promoted more
careful consideration of the costs and benefits associated with biological control. The barriers to the implementation of classical and augmentative biological control with exotic natural enemies
now are sometimes difficult and, as a consequence, the numbers of classical biological control
programs and releases have decreased significantly. Based in part on this new, more careful
approach, classical biological control programs more recently undertaken are increasingly aimed
at controlling especially damaging invasive arthropod pests that otherwise cannot be controlled.
We examine evidence for these revised procedures and regulations aimed at increasing success
and minimizing risk. We also discuss limitations linked to the apparent paucity of postintroduction
monitoring and inherent unpredictability of indirect effects.
