Survey of Native and Honey Bees from Agricultural Brentwood and their Constructed Bee Gardens in Northern California, 2010-2018

Abstract

In 2009 the USDA-NRCS asked the Urban Bee Lab at the University of California, Berkeley if urban bee-flower knowledge could be used to attract native bees to farms in Brentwood, Contra Costa Co. in Northern California. The overarching question was, could native bees play a role in supplementing honey bees by providing pollination services for crop flowers? If so, how many native bee species were visiting farms and how frequently did they occur?Eight small farms (4-60 ha) were selected to investigate this question; four were control and four were treatment farms where bee habitat gardens were constructed. Habitat gardens were stocked with native and non-native ornamental plants known to attract native bees (and honey bees).Bees were monitored yearly in spring at each farm from 2010-2016 to evaluate species richness and abundance, which yielded several findings:I. Farms near urban areas and a creek were consistently more attractive to diverse and abundant bee speciesII. Inconsistent bee garden maintenance and major changes in farm operations in other farms resulted in consistently lower measurements of bee richness and abundanceIII. Over the seven-year monitoring period, 144 bee species were recorded among all farmsIV. Nearby urban areas had most of the same species as the agricultural areas, suggesting a relationship of bees moving between two areasV. A total of 23 diverse native bee species were recorded from apple, berry, and cherry flowers, and many of them in substantial numbers, indicating that native bees were providing pollination servicesFinally, maintaining frequent professional contact with growers was considered crucial in conducting research over the long term. These contacts were also critical in designing outreach packages to growers who expressed interest in applying our native bee findings to their farming operations.