Autumn H. Smart Robert S. Cornman Michael Simanonok Deborah D. Iwanowicz Clint Otto 2020 <p>Managed and wild pollinators are critical components of agricultural and natural systems. Despite the well-known value of insect pollinators to U.S. agriculture, <i>Apis mellifera</i> (Linnaeus, 1758; honey bees) and wild bees currently face numerous stressors that have resulted in declining health. These declines have engendered support for pollinator conservation efforts across all levels of government, private businesses, and nongovernmental organizations. In 2014, the U.S. Department of Agriculture (USDA) and the U.S. Geological Survey initiated an interagency agreement to evaluate honey bee forage across multiple States in the northern Great Plains and upper Midwest. The long-term goal of this study was to provide an empirical evaluation of floral resources used by honey bees, and the relative contribution of multiple land covers and USDA conservation programs to bee health and productivity. Our multi-State analysis of land-use change from 2006 to 2016 revealed loss of grassland and increases in corn and soybean area in North and South Dakota, representing a significant loss of bee-friendly land covers in areas that support the highest density of summer bee yards in the entire United States. Our landscape models demonstrate the importance of the Conservation Reserve Program in providing safe locations for beekeepers to keep honey bees during the summer and highlights how land use in the northern Great Plains has a lasting effect on the health of honey bee colonies during almond pollination the subsequent spring. Our multiseason, multi-State genetic analysis of honey bee-collected pollen revealed <i>Melilotus</i> spp., Asteraceae, <i>Trifolium</i> spp., Fabaceae, <i>Sonchus arvensis</i>, <i>Symphyotrichum cordifolium</i>, and <i>Solidago</i> spp. were the top taxa detected; <i>Melilotus</i> spp. represented 42 percent of all detected taxa. <i>Symphyotrichum cordifolium</i>, <i>Solidago</i> spp., and <i>Grindelia</i> spp. were the top native forbs detected in honey bee-collected pollen. We also conducted plant and bee surveys on private lands enrolled in the Conservation Reserve Program and Environmental Quality Incentives Program. In general, we found significant variability in floral resources and pollinator utilization across USDA programs and practices. On average, greater than 75 percent of honey bee flower observations on private lands enrolled in a USDA conservation program were on non-native forbs, whereas 33 percent of wild bee flower observations were on non-native forbs. <i>Melilotus officinalis</i> and <i>Medicago sativa</i> were the most visited by honey bees, wherease <i>Medicago sativa</i> and <i>Helianthus maximiliani</i> were the most visited by wild bees. Our analysis of nectar dearth periods in June and September for honey bees revealed that although <i>Melilotus officinalis</i> and <i>Medicago sativa</i> were highly visited, less common native forb species such as <i>Ratibida columnifera</i>, <i>Agastache foeniculum</i>, and <i>Gaillardia aristata</i> were preferred species. However, these preferred species were relatively rare on the landscape and are, therefore, unlikely to make up a sizable part of the honey bee diet. In addition to our empirical results, we also showcase how the U.S. Geological Survey Pollinator Library, a decision-support tool for natural resource managers, can be used to design cost-effective seeding mixes for pollinators. Collectively, the results of this research will assist USDA with maximizing the ecological impact and cost-effectiveness of their conservation programs on pollinators in the northern Great Plains.</p> application/pdf 10.3133/ofr20201037 en U.S. Geological Survey Forage and habitat for pollinators in the northern Great Plains—Implications for U.S. Department of Agriculture conservation programs reports