Author
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Brown, Mark |
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Submitted to: Oecologia
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/27/2002 Publication Date: 4/1/2003 Citation: N/A Interpretive Summary: The practice of introducing foreign species of biological control organisms to control pests has come under attack because of ecological considerations of the possible harmful effects on natural environments. This study was conducted to examine the effects of an introduced ladybug (a predator of aphids) on the ecology of apple orchards. Data from three experiments were used to document the aphid predators on apple prior to th arrival of the Asian ladybug and after its arrival. The only negative impact on another species was found to be on the abundance of the seven- spotted ladybug, another introduced species. A secondary effect of the reduction in seven-spotted ladybugs was that native ladybugs were found to be more abundant than prior to the invasion by the Asian ladybug. There were no harmful effects of the Asian ladybug invasion on the natural apple orchard environment. This information will be used by ecologists and biological control practitioners, especially APHIS, to evaluate the impact of future releases of foreign aphid predators for biological control projects. Technical Abstract: The effects of the invasion of an exotic predator, Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae), were investigated using three data sets on the ecology of aphid predators on apple. One data set was collected prior to the H. axyridis invasion, in 1992, and two others, in 1996 to 1997 and 1999 to 2000, were collected after the invasion. Except for one year, 1999, H. axyridis was the dominant coccinellid, replacing the formerly dominant Coccinella septempunctata L. (Coleoptera: Coccinellidae), another exotic species. The dominance of H. axyridis was greater among larval coccinellids than among adults. There was no apparent effect of the H. axyridis invasion on abundance of the predator, Aphidoletes aphidimyza (Rondani) (Diptera: Cecidomyiidae) and a possible positive effect on the abundance of chrysopids (Neuroptera: Chrysopidae). The data indicate that the interaction between the two exotic species, H. axyridis and C. septempunctata, may be allowing native coccinellids to become more abundant on apple than when C. septempunctata was the only dominant coccinellid. |
