Submitted to: European Journal of Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 12/1/2007
Publication Date: 7/3/2008
Citation: Brown, M.W., Matthews, C. 2008. Conservation biological control of spirea aphid, Aphis spiraecolia (Hemiptera: Aphididae), on apple by providing natural altervative food resources. European Journal of Entomology. 105:537-540. Interpretive Summary: Spirea aphid is the most serious aphid pest of apples and requires a preventative insecticide spray to prevent damage to fruit and trees. If biological control could be reliable there would be a reduction in insecticide use and more sustainable apple production. This study was done to test the possibility of increasing biological control by interplanting peach into apple orchards. Peach trees have extrafloral nectar glands that are attractive to lady beetles. There was no difference in biological control of spirea aphid in the orchard but lady beetles did arrive in the apple orchard earlier in the presence of peach trees. Using potted peach trees it was shown that biological control of spirea aphid on trees adjacent to the peach trees was greater than on trees more distant. It is concluded that interplanting the apple orchard with peach trees bearing extrafloral nectar glands does enhance some aspects of the interaction between H. axyridis and spirea aphids but it does not lead to increased levels of biological control. These results will be used by orchard IPM practitioners and extension agents to provide advice to growers who are interested in more sustainable pest management practices.
Technical Abstract: Enhancing biological control in orchards is an efficient way to control insect pests when effective. 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, the most important predator. Two pairs of apple orchards, each with 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 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 was tested comparing biological control on sentinel spirea aphid colonies on apple trees surrounding a cluster of potted peach trees, or a cluster of apple trees as a control. Only the closest spirea colonies to the potted peach trees, on trees within 3m, showed an increase in biological control. Although there was some indication of enhancement of the interaction between adult H. axyridis and spirea aphids, there was no overall detectable increase in biological control by adding alternative food resources in the form of peach trees bearing extrafloral nectar.