Aphid species and associated natural enemies in field crops: what about the invasive ladybird Harmonia axyridis (Coleoptera: Coccinellidae)?

Following the introduction in the 80's of the invasive coccinellid species Harmonia axyridis (Pallas) in Europe, several studies have begun to focus on the interactions with other aphid predator species. In this study, aphids and associated predators were sampled to determine their relative abundance in four agricultural crops (broad bean, corn, potato, and wheat) in Belgium during 2010 and 2011. The Moericke trap was used to quantify the mean number of aphids and aphid predators from May to September in both years. A total of 28 aphid species and 21 aphidophagous species were observed. In both years, H. axyridis was among the most abundant aphidophagous predators in all four crops, and was the second most abundant coccinellid species after Coccinella septempunctata L. The community of aphidophagous species was similar across all four inventoried crops. However, the highest population densities of this alien species were recorded in broad bean and potato crops, which also hosted the highest aphid population densities. In conclusion, this study demonstrates that the communities of aphid predators are highly diversified in the agroecosystems, despite the high occurrence of H. axyridis, an introduced predator that has become well established in this environment.