Evaluating Agroecosystem Quality through Arthropod Interactions in Pennsylvanian Cash Crop Production Systems
Open Access
- Author:
- Adam, Jared
- Graduate Program:
- Entomology
- Degree:
- Master of Science
- Document Type:
- Master Thesis
- Date of Defense:
- June 26, 2024
- Committee Members:
- John Tooker, Thesis Advisor/Co-Advisor
Sara Hermann, Committee Member
Gary Felton, Program Head/Chair
John M Wallace, Committee Member - Keywords:
- Cover crop
no-till
QBS-ar
spiders
pest control
conservation biological control
slugs
agroecosystem - Abstract:
- During the last 60 years in the United States, agricultural production and demand has increased, while total acres farmed has remained relatively constant. The increased demand has led to environmentally damaging agricultural and pest management strategies. This thesis examines the effects of multiple crop production practices on pests and natural enemies. To do this, I have split my thesis into three chapters, each of which examines an aspect of agroecosystem resiliency and quality in modern Pennsylvanian crop production systems. Here, resiliency refers to an agroecosystem’s ability to withstand stresses (e.g., pest populations) without the use of preventative-pest management strategies while practicing IPM. In Chapter 1 of my thesis, I evaluate the effects of planting into a living cereal-rye (Secale cereal L.) cover crop on conservation biological control of multiple pests within corn (Zea mays) and soybean (Glycine max). In the mid-Atlantic, United States, Chesapeake Bay watershed region, the wide use of preventative-pest-management strategies (E.g., seed treatments and tillage) can have serious negative effects on the environment. To mitigate environmental risks, minimal tillage, no-till, and cover cropping practices have been evaluated by extension personnel and adopted by row-crop growers in the region and the United States. While these practices can be effective in reducing run off, reducing pest pressure, increasing diversity, and bolstering resiliency of an agroecosystem, little work has been done to evaluate the role planting into a living cover crop (planting green; PG) has on pest-plant-predator interactions. My goal in this chapter was to determine if planting green can lower overall pest pressure, reduce slug populations, increase predation by natural enemies, and increase yield. I recorded minimal changes in overall pest abundance or pressure, where the multiple-pest damage was the only instance to have more damage in the planting-green treatment. Slug populations only increased with cover-crop biomass in corn plots during the spring of 2021. For predation, higher cover-crop biomass treatments had higher levels of attacked prey, with the highest predation levels occurring later in the season. Lastly, I recorded no differences in yield among treatments. This study demonstrates that planting green can be an effective –conservation based– approach to pest management for row-crop growers. In Chapter 2, I evaluate the role of generalist-spider predators and their contributions to pest control in soybeans. Integrated Pest Management (IPM) within soybeans relies on natural enemies, typically generalist predators, to keep invertebrate-pest populations below economic thresholds. Due to the complex nature of agroecosystems, seldom can one natural enemy contribute to the bulk of pest control. Spiders are ubiquitous insect-feeding predators present in almost all terrestrial ecosystems. Depending on the taxa, spiders deploy several means of prey capture which allows them to exploit a variety of niches within habitats. As a result, spiders have potential to contribute positively to pest control within modern soybean systems managed with Integrated Pest Management (IPM). In this chapter, my goal is to determine the most abundant natural enemies within modern Pennsylvanian soybean systems. Furthermore, I attempt to quantify the role that spiders play in invertebrate-pest control through the manipulation of pest and predator populations in the field. I determined that spiders are the most abundant predators of soybeans in Pennsylvania and that the family Thomisidae had the greatest abundance of all spiders. While pest populations did not decrease with an increase in spider populations, it appears that spider populations respond proportionally to prey abundance. Time of season influenced spider populations and most individuals sampled came from mid-late season sampling periods (July-August). This study highlights spiders as the most abundant predators within modern soybean systems and that current row-cropping systems do not support their populations during the early season. In Chapter 3 of my thesis, I evaluate the biological quality of soils under different crop management practices using soil invertebrates and the Biological Soil Quality index-arthropod (QBS-ar). We rely on soils for many things including food production and environmental improvement. Soils of course support crop production, but also extend to the improvement and support of environmental quality. One way environmental quality can be improved by soils is through support of soil-dwelling fauna. To support biological diversity of soil-dwelling fauna soils must be of high quality. Soil quality refers to measurable attributes that relate to the capacity of soil to function without a negative interaction with the environment. Current tests for soil quality use multiple chemical, physical, and biological attributes (e.g., bulk density, nitrogen availability, and microbial respiration). These attributes often reveal important information to growers on how to maintain and increase crop quality and yield. What these tests do not cover are direct links to biological quality. Specifically, the biological assessment of soils subject to different crop management practices. The QBS-ar index is a reliable method for evaluating the biological quality of an ecosystem. The QBS-ar index scores biological quality based on the morphological adaptations of soil-dwelling (edaphic) invertebrates within. My goal was to determine which suite of row-crop practices produced the highest QBS-ar values and to determine which factors most influenced soil-invertebrate abundance and QBS-ar values. Along with this, I set out to test if the termination timing of a cover-crop influenced QBS-ar values and overall soil-invertebrate abundance. I found no change in QBS-ar value based on cover-crop biomass or system type (organic vs. conventional). I did, however, record differences in QBS-ar values based on tillage practices. Fields subject to no-till had higher QBS-ar values than fields that underwent any form of tillage pre-cash-crop planting. Additionally, twenty-six of the total twenty-eight recorded QBS-ar scores fell below the high-quality threshold. My results display a trend that the sampled row-crop-management practices seldom aid in bolstering biological quality of soils.