Hoverflies ( Diptera: Syrphidae) benefit from a cultivation of the bioenergy crop Silphium perfoliatum L. ( Asteraceae) depending on larval feeding type, landscape composition and crop management.

An increasing production of annual bioenergy crops such as maize has led to regional land-use changes, causing further shortages of already scarce floral resources for pollinators. Diversification of energy crop production with flowering crops is discussed as a mitigation strategy. The perennial Silphium perfoliatum, characterized by a flowering period between July and September, represents a promising candidate crop., The present study aimed to investigate the management and landscape conditions under which a cultivation of S. perfoliatum could be an effective measure for pollinator conservation. In this context, hoverflies served as suitable indicators as a result of the different feeding behaviours of adults (floral resources) and larvae (mostly zoophagous or microphagous)., We compared abundance and species richness of adult hoverflies in 15 flowering S. perfoliatum fields in Germany with that in neighbouring habitats (maize fields, ditches/brooks and forest edges) and tested whether the landscape composition influenced local abundance and species richness in S. perfoliatum fields depending on larval feeding type., Only microphagous hoverflies were more abundant in S. perfoliatum fields than in neighbouring habitats, primarily in mid- September. This might be explained by the different activity periods and adaptations to flower traits of the two hoverfly groups. Although the abundance of zoophagous hoverflies was positively influenced by a higher crop diversity, the abundance and species richness of microphagous hoverflies responded positively to higher proportions of semi-natural habitats in the surroundings., Silphium perfoliatum can support certain hoverfly groups when it is harvested late to ensure a flower supply through to September and when semi-natural habitats are maintained in agricultural landscapes. [ABSTRACT FROM AUTHOR]