Individual study: Sown annual forage plants on farmland receive a diversity of insect visitors, at Rothamsted Research, Hertfordshire, England
Carreck N.L. & Williams I.H. (2002) Food for insect pollinators on farmland: insect visits to flowers of annual seed mixtures. Journal of Insect Conservation, 6, 13-23
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Plant dedicated floral resources on farmland
Carreck & Williams (2002) evaluated a sown mix of six annual flowering species: cornflower, common mallow Malva sylvestris (both native), borage, buckwheat, marigold Calendula officinalis and phacelia as forage for insects, in four plots at Rothamsted Research, Hertfordshire, England. The mix attracted 16 bee species, the most numerous insects being honey bee Apis mellifera and red-tailed bumblebee Bombus lapidarius/B. ruderarius (not distinguished in the study). 97% of all bumblebee visits were to phacelia and borage, 67% of all solitary bee visits were to marigold. The common carder bee B. pascuorum and garden bumblebee B. hortorum (both common long-tongued species) were recorded in relatively low numbers.
Plant nectar flower mixture/wildflower strips
A replicated study in 1996 and 1997 in Hertfordshire, UK (Carreck & Williams 2002) (same study as Carreck et al. 1999) found that plots sown sequentially from mid-April to mid-July with a mix of six annual flowering species (cornflower Centaurea cyanus, common mallow Malva sylvestris (both native), borage Borago officinalis, buckwheat Fagopyrum esculentum, marigold Calendula officinalis and phacelia Phacelia tanacetifolia) provided continuous forage for pollinators from mid-June to mid-November. The mix attracted 15 bee (Apidae), 17 fly (Diptera) and six butterfly (Lepidoptera) species and the common wasp Vespula vulgaris. The most numerous insects were the honey bee Apis mellifera and red-tailed bumblebee Bombus lapidarius/B. ruderarius (not distinguished in the study). Abundance of flies varied over the season while abundance of butterflies was low. Butterflies and bumblebees Bombus spp. preferred borage and phacelia, while solitary bees and flies preferred marigold. Mallow and buckwheat did not contribute much to flower density or pollinator diversity. Four plots (22 x 14 m or 20 x 13 m) were sown each year (91 or 22 kg/ha) at monthly intervals, then harrowed and irrigated as necessary. Flower density was recorded weekly in four random 1 m2 quadrats in each plot. Pollinators were recorded in the outer 3 m of each plot on 21-34 days from mid/end of-June to end of October/beginning of November.