Chapter

Pros and Cons of Biological Control

DOI: 10.1007/978-3-540-36920-2_23

ABSTRACT 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.

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    ABSTRACT: During 1994 -1999 several hundred thousands of Harmonia axyridis adults were released at various cultivations infested by aphids (citrus, vegetable and bean crops, maize, etc.) or in urban places on ornamental plants in central and southern Greece (mainly Attica and Peloponnessos region) as well as on several islands. During 1995-2007, samplings were conducted in some areas, in spring just before any new releases, in order to determine if H. axyridis overwintered in the field. In spring 1995 (the year that followed the first releases) as well in spring 1996-97 and 2000-07, no presence of H. axyridis was recorded in any of the orchards where the predator had been released. Only in spring 1998 and 1999 small colonies (

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