Effects of pastures on early spring pollinator communities around canola (Brassica napus) production

Production of canola as a biofuel and cooking oil is expanding with unknown consequences for native insect pollinators. Canola is generally planted in rotation with winter wheat in the South Central US and is an early-blooming, floral resource for many bee and butterfly species; however, each field has a 90% likelihood of being treated with insecticides known to be harmful to bees and butterflies. In the spring of 2011, 2012, and 2013 we captured pollinators from canola fields and wheat fields, in areas with and without adjacent pastures in order to document the abundance and richness of pollinator species and to elucidate the influence pastures have on bee and butterfly abundance and diversity around canola fields. Trap nests were also placed at sites to elucideate bee foraging and development in 2013 and 2014. Our data show eight bee species are the most abundant and bee richness is highest in canola fields near pastures and lowest in wheat fields without pastures.  Furthermore, bumblebees were more common at sites with pastures than in areas without pastures. Trap nest data showed parasitism to be more common in areas without pastures. Six butterfly species were the most frequent at our sites, mainly in the family Nymphalidae. Pasture did not significantly influence pollinator abundance overall, but did increase the likelihood of the occurrence of specific species.