Degree Type


Date of Award


Degree Name

Doctor of Philosophy





First Advisor

Matthew Elliot O'Neal


Managed honey bees are the most important pollinator worldwide, contributing to pollination of numerous crops, and they highly valued for their production of honey. The USA and Europe have experienced high colony losses in recent years, impeding the sustainable development of the beekeeping industry and endangering food safety due to its heavy reliance on insect pollination. The extensive production of crops across large areas of the U.S. and Europe have introduced multiple biotic and abiotic stressors for bees, including poor forage, pathogens and parasites, and pesticides, contributing to high colony losses. The Midwestern U.S., as a region with extensive monoculture-based agricultural production, has also been identified as a critical area for pollinator declines, making this area an important target area for honey bee health improvement.

For my doctoral research, I focused on honey bee health in the state of Iowa, at the epicenter of extensive agricultural production in the Midwestern U.S. I determined how the diversity and abundance of pollen, the main dietary source of proteins, lipids and micronutrients for honey bees, was affected by agricultural vs. natural foraging habitats, floral resources, and conservation practices (i.e. cropland integrated with strips of prairie vegetation). I also assessed whether the most common pollen types collected by honey bees in agricultural landscapes in central Iowa improved one aspect of honey bee health, resistance to virus infection. In addition, I used multi-year honey bee pollen collections to understand how annual weather fluctuations affect pollen collection. Finally, I determined if overall colony health would be improved with the integration of prairie strips into cropland as apiary sites.

My findings provided several novel insights into honey bee landscape nutrition in agroecosystems. First, I found that low cultivation landscapes (lower percentage of cropland) did not improve pollen forage for honey bees compared to high cultivation landscapes (higher percentage of cropland). Legumes were the major source of pollen in agricultural landscapes, small increase in diversity of plants used as a source of pollen enhanced the survival of honey bees infected with viruses. Pollen collected by honey bees did not vary depending on land use types adjacent to honey bee colonies, with no marked differences between apiaries placed in soybean fields, diversified fruit and vegetable farms, and prairies. On a year-to-year basis, co-occurrence of drought and high temperature conditions had the potential to reduce pollen abundance available to honey bees. With respect to conservation habitat, restored prairies were important forage sources for honey bees, primarily in the late growing season period when crops and nonnative weedy plants ceased blooming. Integrating prairie plants into cropland (namely prairie strips, which are typically smaller than traditional prairie restorations or remnants) significantly improved pollen abundance and overall health of honey bee colonies across the growing season, compared to cropland without prairie strips. Overall, these results highlighted the potential for integrating beekeeping, crop production, and conservation practice, i.e. integrating native plants in to cropland, as a sustainable model for simultaneously enhancing honey bee health, agriculture, and biodiversity.


Copyright Owner

Ge Zhang



File Format


File Size

240 pages