Restricted (Penn State Only)
Mc Tish, Sarah
Graduate Program:
Master of Science
Document Type:
Master Thesis
Date of Defense:
March 15, 2019
Committee Members:
  • John Frazier Tooker, Thesis Advisor
  • Heather D Karsten, Committee Member
  • Heather Elise Gall, Committee Member
  • Mary Ellen Barbercheck, Committee Member
  • Neonicotinoid Insecticides
  • Pest Management
  • Diversity
  • Agriculture
  • Water Runoff
  • Slugs
  • Ground Beetles
As agricultural intensification continues in the United States there is a need for developing and using sustainable practices that maintain productive yields while also protecting the environment. For my first chapter, I compared two crop rotations, one representative of a diverse dairy rotation typical of the Mid-Atlantic United States. More specifically, over two field seasons, I compared a 2-yr low plant diversity, preemptive pest control rotation to two, 6-yr high plant diversity, integrated pest management (IPM) rotations and how these different rotations influenced pest and predator populations, with a focus on slugs and their ground beetle predators. Overall, I found that in many cases increasing plant diversity within rotations and decreasing insecticide use suppressed pest populations and fostered higher predator populations. In 2017, the maize grown for grain in the high-diversity, IPM rotation produced higher yields than the low-diversity, preemptive pest control rotation. Also, in 2017, soybean yields were equal between these rotations. My results suggest that increasing plant diversity within cropping rotations and using integrated pest management with reduced insecticides can be an effective means for controlling pests to remain below economically damaging levels. Because of my interest in reducing insecticide use in Chapter One, I wanted to explore possible negative consequences of one of the preventative insecticides used in the low-diversity, high insecticide input rotation: the neonicotinoid insecticides. For Chapter Two, I examined the potential for these insecticides to be transported from agricultural fields to nearby aquatic environments. These highly water-soluble insecticides, used as seed coatings, are translocated throughout growing seedlings, but very little of the active ingredient applied to seeds is actually taken up by the growing seedling. The majority of the active ingredient is then retained in soil, where it is susceptible to transport via surface runoff, leaching to groundwater, biodegradation, sorption to soil, and drift as planting dust. Because neonicotinoids are highly water-soluble, they have a high potential to impact water quality and pose a risk to aquatic ecosystems, making it critical to understand how neonicotinoids leave crop fields in water and at what concentrations. To determine these concentrations of active ingredient applied to seed coatings leaving the crop field in water, I used field lysimeter plots to collect surface and subsurface water runoff from corn fields planted with seeds coated with the neonicotinoid thiamethoxam. Samples were then analyzed for concentrations of thiamethoxam and its degradant clothianidin using HPLC/MSMS-Orbitrap. These concentrations paired with water flow data provide the mass loss of active ingredient that occurs with each runoff event. After collecting surface and subsurface runoff, I found that 1.3% of thiamethoxam and its metabolite clothianidin are lost to the surrounding aquatic environment where it could have negative unintended consequences.