Determining the Influence of Ecosystem Complexity and Latitudinal Position on the Ability of Biological Control to Offset Use of Pesticides in a Warming Climate

EPA Grant Number: FP917780
Title: Determining the Influence of Ecosystem Complexity and Latitudinal Position on the Ability of Biological Control to Offset Use of Pesticides in a Warming Climate
Investigators: Gray, Hannah L
Institution: University of Minnesota
EPA Project Officer: Lee, Sonja
Project Period: September 1, 2015 through August 31, 2018
Project Amount: $132,000
RFA: STAR Graduate Fellowships (2015) RFA Text |  Recipients Lists
Research Category: Academic Fellowships


Increasing minimum daily temperatures in the United States already is associated with higher insecticide use, indicating a break-down in natural biological control services and increase in pest pressure as compared to cooler latitudes. In order to minimize pesticide usage in Northern states as daily minimum temperatures rise, research needs to address how levels of biological control vary in relation to latitude and ecosystem complexity. The objective of this research is to determine whether the relative influence of ecosystem complexity on predation services varies based on daily minimum temperatures in order to assess the potential of biological control to offset pesticide usage in the future.


I will examine latitudinal variation in predation pressure across four Midwestern states. Prairie ecosystems will serve as my natural ecosystems, and at each site I will use natural prairies and polyculture and monoculture farms to compare ecosystem complexity. Sites will range from 44 to 36°N and include the Kellogg-Weaver Dunes (MN), Lake Ahquabi State Park (IA), Konza Prairie (KS), and Tallgrass Prairie Preserve (OK). Three times through the growing season and over two years I will experimentally estimate relative predation pressure across the latitudinal gradient and ecosystem types. Relative predation pressure will be assessed using a set number of sentinel plasticine caterpillars in each ecosystem for 24-hour periods. Additionally, I will conduct biodiversity surveys that focus on species abundance and functional traits for plant and insect species (especially natural enemies) to help explain variation in predation rates. Finally, I will confirm the results with the plasticine caterpillars with real Trichoplusia ni. caterpillars at one location.

Expected Results:

Daily minimum temperatures play a crucial role in insect behavior and therefore their interactions with other organisms in the environment. I expect that I will find the highest rates of predation in natural prairie ecosystems at the lowest latitude in Oklahoma, but that in simplified monoculture and polyculture ecosystems this pattern will not hold, due to the reduction of non- crop resources necessary to sustain biocontrol agents. I expect to find the effect size of ecosystem simplification on predation rate to be positively correlated with latitude and daily minimum temperature, underscoring the importance of maintaining ecosystem complexity to provision biological control services in a warming climate.

Supplemental Keywords:

predation, biological control, latitude, ecosystem simplification, pesticides