Date of Graduation

7-2021

Document Type

Dissertation

Degree Name

Doctor of Philosophy in Entomology (PhD)

Degree Level

Graduate

Department

Entomology and Plant Pathology

Advisor/Mentor

Joshi, Neelendra K.

Committee Member

Burke, Joan M.

Second Committee Member

Leslie, Timothy

Third Committee Member

Loftin, Kelly M.

Keywords

Bees; Livestock; Non-bee pollinators; Pasture; Pollinator

Abstract

Pollinators are important for fertilization, setting fruits, and seed development of more than 78% of the flowering plants that provide food for human beings and other species. Use of pollinators to maximize crop production is a proven agricultural practice; however, it has been less explored in livestock forage production systems. This study investigated pollinator abundance and diversity in pastures using different sampling methods and determined the impact of different pasture management practices on insect pollinators in a livestock pasture ecosystem. In Chapter 2, utility of four different colors of pan trap (blue, green, yellow, and purple) for sampling bees in a livestock pasture ecosystem of native forage species was examined. Blue color traps were the most attractive to bees followed by purple, yellow and green color traps. In Chapter 3, vanes with different colors (dark blue, bright blue, dark yellow, bright yellow, purple, and red) were designed and evaluated for their light reflectance properties and attractiveness to wild bees in livestock pasture. Bright blue traps captured the highest number of individuals and species of bees. This could be due to appropriate match between the visual spectrum of bees and light reflectance spectrum of vanes. Bees responded similarly to traps with other colors of vanes, except for red vane traps, which captured the lowest number of bees. In Chapter 4, impacts of grazing native forb and grasses on insect pollinators and other arthropod communities in a pasture system was determined. The abundance, diversity, and evenness of bee communities and other insects were greater in non-grazed plots as compared to grazed pasture plots. However, species richness, as measured by rates of species accumulation relative to sampling effort, was not different among treatments. In Chapter 5, a two-year study assessed how organic and non-organic pasture management practices affect bee abundance and diversity in pastures. Bee diversity, abundance, and species richness of bees (as measured by rarefaction curve) were similar between pastures under organic or non-organic management. Different factors such as low availability of floral resources in organic pastures, use of synthetic fertilizers (to promote the growth of plants) and herbicides for weed management in non-organic pastures might have affected abundance and richness in organic and non-organic pastures. In Chapter 6, impact of commercial native forb/legume/grass (FLG) or warm season grasses (WSG; equal mix of Andropogon gerardi, Tripsacum dactyloides, and Sorghastrum nutans) on bees and non-bee insect communities in livestock pasture was determined. Total number of bees collected was higher in FLG than in WSG (3380 in FLG vs 3158 in WSG). Similarly, 3692 non-bee insects were collected from FLG whereas WSG contained 2346 non-bee insects. Findings from these studies will be helpful in selecting appropriate sampling methods for monitoring bees and other insect communities and also be helpful in developing pollinator-friendly pastures that support diversity of native bee species and other beneficial insects in livestock pasture ecosystems.

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