Author
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Brown, Mark |
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MATHEWS, CLARISSA - SHEPHERD UNIVERSITY |
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Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 6/21/2007 Publication Date: 10/1/2007 Citation: Brown, M.W., Mathews, C.R. 2007. Conservation biological control of rosy apple aphid, Dysaphis plantaginea (Passerini) in eastern North America. Environmental Entomology. 36(5):1131-1139. Interpretive Summary: The rosy apple 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 survey the existing biological control of this aphid and to test the possibility of increasing biological control by changing the orchard management plan. Unsprayed research orchards were sampled from 1997 to 2006 to examine the level of biological control and to test the effect of interplanting either 50%, 9% or 0% peach trees in the apple orchard on biological control. There were high rates of biological control in early spring, prior to apple bloom, with 98% loss of aphid colonies. After bloom there was not adequate biological control to control the aphids that remained. Predation by the multicolored Asian lady beetle was responsible for the early season control of rosy apple aphids. Orchards interplanted with 9% peach trees had higher predation rates than either the 50% or 0% interplanted orchards, with no aphid colonies surviving past bloom. It is concluded that interplanting the apple orchard with 9% peach trees bearing extrafloral nectar glands will result in reliable biological control of rosy apple aphid. 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: Because of the potentially serious damage rosy apple aphid, Dysaphis plantaginea (Passerini) (Homoptera: Aphididae), can cause to apple fruit and branch development, prophylactic insecticides are often used for control. If biological control could be relied on, the amount of pesticide applied in orchards could be reduced, at least in some years. This study examined biological control of rosy apple aphid in eastern West Virginia and the potential for enhancement through conservation biological control, in particular the effect of interplanting extrafloral nectar-bearing peach trees. By 20 days after first bloom only 2% of fundatrices initially present survived to form colonies based on regression of data from 687 colonies sampled in 2002, 2004 and 2005. Exclusion studies showed that a conservative estimate of this early mortality that was due to predation was 62%. The major predator responsible for the early decline in rosy apple aphid colonies appeared to be adult Harmonia axyridis (Pallas) (Coleoptera: Coccinellidae). Early season aphid mortality rate was significantly greatest in orchards interplanted with 9% peach trees and lowest in orchards interplanted with 50% peach trees. Monoculture apple orchards had an intermediate level of mortality that was significantly different from that in either interplanted orchard. The number of leaf curl colonies in the 50% interplanted orchards was lower than in monoculture orchards, which in spite of the lower early mortality rate in monoculture orchards indicates a preference of alate oviparae for more diverse habitats, supporting the resource concentration hypothesis. Predation and parasitism after the formation of leaf curl colonies was not adequate to control rosy apple aphid populations. It is recommended that interplanting apple orchards with 9% peach trees be used as a management technique to increase biological control, at least for rosy apple aphids, and possibly to reduce the need for one or more insecticide applications. |
