Date of this Version
Daniel SR. 2021. Investigating the Role of Spiders in Integrated Pest Management for Biological Control of Nebraska Crop Pests. Master's thesis, University of Nebraska-Lincoln, Lincoln, Ne.
As generalist predators, spiders are capable of fulfilling a wide variety of ecological niches allowing them to intercept and prey upon an array of insect species. This characteristic could be particularly advantageous within agricultural ecosystems. This project sought to reveal the composition and abundance of spider communities within cornfields in western Nebraska and the impact of agronomic practices on those communities as well as determine the potential for spider predation upon two key pests of corn. Spiders were collected from eight corn fields from May to August 2017 and four corn fields from May to August 2018. Additionally, the populations of two important pests of corn, western corn rootworm (Diabrotica virgifera virgifera) and western bean cutworm (Striacosta albicosta), were sampled to determine prey availability. During the course of this study, a total of 1,011 spider specimens composed of 15 families, 34 genera and 54 species were collected from the 12 field sites for both years combined. Of the total specimen count, 300 (30%) were immatures. Two families, Lycosidae and Linyphiidae, made up 60% (n = 605) and 24% (n = 244) of all specimens collected, respectively. Gnaphosidae (n = 36) and Thomisidae (n=36) were the third most common families collected, representing 4% each of all spiders collected. The impact of three agronomic practices (tillage, crop rotation and insecticide use) on spider species diversity and evenness was evaluated. Species evenness was not significantly affected by any of the practices while species diversity was significantly impacted by insecticide use alone. Pest population sampling revealed presence of both western corn rootworm and western bean cutworm in the sampled fields. Field-collected Thomisidae and Lycosidae were screened for target prey DNA: none of the screened thomisids tested positive for S. albicosta DNA while only two lycosids tested positive for D. v. virgifera DNA. While these results indicate no to very low predation of these pests by the selected spider families in the field, a variety of factors including short DNA detectability windows, spider feeding habits and prey availability at the time of spider capture may help to explain these results and illustrate a need for additional studies. These results reveal the abundance and composition of spider communities in Nebraska corn fields as well as the role of spiders within agroecosystems. The results can be utilized to develop improved conservation biological control programs in the future.
Advisors: Julie A. Peterson and Robert J. Wright