Aphids in the genus Uroleucon Mordvilko (Hemiptera: Aphididae) are native herbivores that feed on goldenrod (Solidago spp.) and other Asteraceae in North America. The aphids are potential prey for a wide variety of natural enemies, including native and non-native species of lady beetles (Coleoptera: Coccinellidae). Non-native lady beetles were introduced to aid control of pest aphids in cropland, but some (e.g. Coccinella septempunctata L. and Harmonia axyridis [Pallas]) are known to prey upon Uroleucon aphids in natural and semi-natural settings, raising concerns about their nontarget effects on native aphids. The objective of this study was to estimate non-target risk to Uroleucon aphids from non-native lady beetles. Risk was estimated by evaluating consumption of Uroleucon aphids by lady beetles in no-choice laboratory tests, and by determining incidence of non-native lady beetles within naturally occurring patches of goldenrod and giant sumpweed (Cyclachaena xanthifolia (Nutt.) Fresen.) used by U. nigrotuberculatum (Olive) and U. ambrosiae (Thomas), respectively, in eastern South Dakota during 2009 and 2011. Although lady beetles substantially lowered populations of Uroleucon aphids in no-choice laboratory tests, they were infrequently associated with natural occurrences of the aphids, with incidence comprised of only four native Hippodamia convergens Guérin-Méneville and one non-native C. septempunctata on 185 aphid-infested sample units in relatively small patches of goldenrod and giant sumpweed. Despite consumption of aphids in laboratory tests, the particularly low incidence of lady beetles in field surveys indicates an empirically small risk of their predation on U. nigrotuberculatum and U. ambrosiae under field conditions.
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