Abstract
Enhancing biological control in orchards is an efficient way to control insect pests. This study investigates the possibility of increasing biological control of spirea aphid by providing alternate food resources, in the form of peach extrafloral nectar, to adult Harmonia axyridis, its primary predator. Two pairs of apple orchards, each having one interplanted with 50% trees bearing extrafloral nectar and one a monoculture, were studied for aphid and predator populations from 1999 to 2005. There were no differences in spirea aphid or predator populations between interplanted and monoculture orchards. However, H. axyridis adults arrived earlier in the interplanted than in the monoculture orchards. In another apple orchard, the effect of peach extrafloral nectar on sentinel spirea aphid colonies surrounding a cluster of potted peach trees, or a cluster of apple trees as a control, was tested in 2007. Only the closest spirea colonies to the potted peach trees, trees within 3 m, showed an increase in biological control. Although there was some indication of enhancement of predation by adult H. axyridis on spirea aphids, adding alternative food resources in the form of peach trees bearing extrafloral nectar resulted in no detectable increase in biological control.
Highlights
Habitat management to increase conservation biological control has become a significant area of research (Landis et al, 2000) and has been proposed as a method to increase sustainability through enhanced biodiversity (Boller et al, 2004)
Adult Harmonia axyridis Pallas (Coleoptera: Coccinellidae) are the most effective predators of spirea aphid in West Virginia USA (Brown, 2004) since it first arrived in eastern North American apple orchards in 1994 (Brown & Miller, 1998)
The food provided by the peach extrafloral nectar may have kept these ladybirds in the orchard so that when spirea aphids migrated into the orchard H. axyridis adults were present and did not need to respond from more distant habitats
Summary
Habitat management to increase conservation biological control has become a significant area of research (Landis et al, 2000) and has been proposed as a method to increase sustainability through enhanced biodiversity (Boller et al, 2004). Interplanting species of fruit trees bearing extrafloral nectaries into apple orchards has been suggested (Brown & Mathews, 2005). Aphis spiraecola Patch, has become the most abundant aphid on apple in eastern North America (Brown et al, 1995). Adult Harmonia axyridis Pallas (Coleoptera: Coccinellidae) are the most effective predators of spirea aphid in West Virginia USA (Brown, 2004) since it first arrived in eastern North American apple orchards in 1994 (Brown & Miller, 1998). The present study was conducted to assess the possibility of increasing biological control of spirea aphid on apple by interplanting peach (Prunus persica Batsch) trees bearing extrafloral nectaries
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