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23 Pros and Cons of Biological Control
Dirk Babendreier
23.1 Introduction
Biological control involves the deliberate introduction of natural enemies for
the control of pest organisms, including insects, weeds and diseases.A general
difference exists between augmentative releases where biological control
agents are used periodically, i.e. once or several times within a season, and
classical biological control where agents are released with the aim of establishment
and, ideally, a permanent pest control.Whereas native candidates are
generally given preference in augmentative biological control, in some cases
exotic species have been used. By contrast, for classical biological control the
rule is that exotic natural enemies are introduced for the control of exotic
pests. Pest species may either interfere with agricultural production without
being invasive per se or may be invasive on a larger scale, thereby threatening
ecosystems and natural reserves. Whereas arthropod biological control generally
applies to the former, it is in the weed control section that biological
control agents are often released to control invasive species. This means that
biological control finds itself in the unique position of being both an important
strategy for the control of alien invasive species and also a route by which
potentially damaging new alien species (i.e. the natural enemies) are themselves
introduced and spread (Chap. 2).
This chapter will briefly review the positive aspects of biological control
and will highlight a few examples. It will further review negative aspects of
biological control introductions. One of the examples where biological control
led to detrimental environmental effects was the introduction of the ladybeetle
Harmonia axyridis, and this case will be outlined in more detail. This
example will also be used to explore some of the population biology mechanisms
which can contribute to the net effects of introduced natural enemies.
Finally, some information on recent developments and improvements in risk
assessment of biological control agents is provided.
Ecological Studies,Vol. 193
W. Nentwig (Ed.)
Biological Invasions
© Springer-Verlag Berlin Heidelberg 2007