Esquivel, Isaac Luis (2020-05). Effects of Landscape Structure on Herbivorous Pests and Native Pollinators in the Cotton Agroecosystem: Implications for Pest management. Doctoral Dissertation.
Thesis
This body of work investigates the role the landscape plays on the spatial relationships of cotton pests and native be pollinators at the local level, with the goal of improving pest management strategies at a larger scale while conserving native pollinators that have potential benefits for cotton production. This will be done through four objectives represented as chapters. In chapter two, I investigated the interplay that edges and ecotone type (agricultural interfaces) have on the populations of cotton fleahopper and verde plant bug and associated cotton injury. Findings indicated that field edge and ecotone type play a significant role in the pest pressure seen within cotton. Land managers should consider the spatial arrangements of fields when developing pest scouting and management strategies. In chapter three, I test the feasibility and applicability of using unmanned aerial systems (UAS's) in detecting cotton fleahopper damage. The data suggest that differences in cotton fleahopper stress on cotton may be reflected in NDVI values, but the form seen may be complicated by the feeding site (immature fruiting bodies) of cotton fleahopper. In chapter four, I investigated potential benefits the native bee M. tepaneca has on cotton production via pollination services. Cotton flowers that were caged and hand-crossed along with flowers exposed to caged M. tepaneca had higher pre-gin weights and post gin weights, compared to those flowers of caged plants excluded from pollinators. This bee-mediated service resulted in a 12.8% seed cotton increase in 2018 and a 32% increase in 2019. In Chapter Five, I investigated the effects of landscape structure on the biodiversity and abundance of native pollinators within the cotton agroecosystem. Bee bowls used over two years, a total of 32 species of native bee pollinators in 13 genera across 3 families were collected. Communities of native bees at crop-crop interfaces tended to be more consistent in the abundance and number of species at each sampling site across samples. On the other hand, sites at semi- natural habitat interfaces contained more species, but abundances varied across samples. This suggests that even in highly large-scale cotton agroecosystems, a community of native bees persists, and some species may even thrive.
