SUPPORTING BOMBUS AND OTHER BEES IN CUCURBITA AGROECOSYSTEMS
Open Access
- Author:
- Treanore, Erin D
- Graduate Program:
- Entomology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- August 10, 2017
- Committee Members:
- Shelby Fleischer, Thesis Advisor/Co-Advisor
Christina M Grozinger, Committee Member
Heather M Hines, Committee Member - Keywords:
- Cucurbita pepo
Bombus
Pollinators
Nutritional Ecology
Pollen
Neonicotinoids
Cover Cropping
Habitat Enhancements
Pollen Nutrition - Abstract:
- The decline of pollinators, in particular bees, has been an extensively researched and discussed topic in the last few decades. This decline was noted in both honey bees and native bee species, with concern increasing for some bumble bee species. A myriad of stressors have been implicated in this decline, but pathogens, pesticides, parasites and loss of habitat resulting in poor nutrition, canvas a majority of suspected and interacting factors. Agricultural land intensification houses a number of these stressors, often resulting in both increased likelihood to pesticide exposure and a loss of access to diverse assemblages of floral resources. Paradoxically, agriculture can also function to provide a large pulse of the floral resources that bees depend on. In this thesis I target this issue by focusing on a commonly found agroecosystem within the Mid-Atlantic region, pumpkin, or Cucurbita pepo, and examine (1) How cover-cropping can be used as a form of floral provisioning to provide additional resources for generalist pollinators (2) The quality of the floral resources provided within these floral provisionings, and (3) Effects of insecticide usage on both Cucurbita pepo and its generalist pollinators. Cucurbita pepo presents a challenging system to work with due to its rotational nature, which creates limitations on the type of floral provisioning that can be used. I examined how a dual-flowering planting (fall-flowering and spring-flowering) using mixtures of common cover-crop species could fit into this system while supporting relevant pollinators. I also observed how various seeding rates affected the floral density of the planting, and how that effect persisted into the behavior of the pollinators. I found that seeding rate did not significantly affect either the floral density, or the behavior of the pollinators, suggesting that growers have flexibility in the seeding rate they use. I then focused on the quality of the floral resources provided in these plantings, e.g., the pollen, to observe how Bombus impatiens fed on this pollen would respond. I approached this by using no-choice bioassays using queenless B. impatiens microcolonies and pollen from pumpkin, two common cover crop species from two plant families commonly visited by Bombus, a multifloral diet, and an artificial honey bee diet. After seven days, I examined the size of their ovaries, their change in weight, and their waxing behavior to gauge their response. I confirmed that adults feed on pollen, and found that pollen quality had a significant impact on the size of their ovaries, as well as ability to produce wax. Lastly I examined the Cucurbita pepo system itself by looking at systemic insecticide usage and possible risks of exposure for Bombus and Apis mellifera. I examined how different methods of neonicotinoid treatment effects the floral display within Cucurbita pepo, and how this persisted into the foraging behavior of the observed pollinators. Looking at plant response, I found that the amount of insecticide applied had a significant effect on the number of flowers produced by the plant. Apis mellifera and Bombus demonstrated alternative preference to treatments, with treatment having a significant effect on foraging behavior of Apis mellifera but not Bombus. By approaching pollinator conservation in an agroecosystem using an integrative approach, I aimed to emphasize the importance of considering all components of an agroecosystem. Although this research was conducted within the Mid-Atlantic, the ideas and concepts can be considered within the context of other systems and regions. These studies and findings in this thesis were meant to improve our understanding and ability to support pollinators through threat mitigation and a more targeted approach to floral provisioning