The response of non-target soil invertebrates to preventive insecticide use in field crops
Open Access
- Author:
- Pearsons, Kirsten
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- June 09, 2020
- Committee Members:
- John Frazier Tooker, Dissertation Advisor/Co-Advisor
John Frazier Tooker, Committee Chair/Co-Chair
Mary Ellen Barbercheck, Committee Member
Andrew R Deans, Committee Member
Ray B. Bryant, Outside Member
Gary Felton, Program Head/Chair - Keywords:
- decomposition
neonicotinoid
insecticide
decomposer
soil invertebrate
litterbag
toxicology - Abstract:
- In the U.S., most field-crop growers deploy insecticides as an insurance measure against insect pests, rather than in response to a known pest infestation. This preventive approach to pest management has led to a global overuse of insecticides, which disrupts pollination, biocontrol, and other ecological services provided by invertebrates. In this thesis, I used entomology, environmental chemistry, toxicology, and ecology to address how preventive pest management affects non-target soil invertebrates. Specifically, I addressed how pyrethroids and neonicotinoids affect invertebrate predators and decomposers in crop fields. Both pyrethroids and neonicotinoids negatively affect predatory and detritivorous soil invertebrates, limiting their contribution to pest control and nutrient cycling. In Chapter 1, I reviewed how sustainable management practices can compensate for and reduce ecological disturbances associated with crop production. I noted that preventive pest management will limit the benefits associated with reducing tillage and planting cover crops. In Chapter 2, I measured neonicotinoid concentrations in field plots that were planted with or without neonicotinoid seed coatings. Neonicotinoids from seed coatings significantly contaminated adjacent untreated field plots, and cover crops did not directly affect neonicotinoid concentrations. In Chapter 3, I assessed the acute toxicity of a neonicotinoid (clothianidin) and a pyrethroid (tefluthrin) to species of non-target soil invertebrates. Carabid beetles and isopods were more sensitive to clothianidin than tefluthrin, spiders were more sensitive to tefluthrin, while millipedes and slugs were insensitive to both. Invertebrates in the same trophic groups responded differently to these insecticides, indicating that the negative outcome of choosing one insecticide over another will depend on the composition of the soil-invertebrate community. In Chapter 4, I conducted a field experiment to compare the effect of neonicotinoid seed coatings and early-season pyrethroid sprays on abundance of macroarthropod decomposers, microarthropods, and decomposition rate. Both insecticides reduced densities of arthropod decomposers and decomposition of plant litter, which could affect long-term residue breakdown and nutrient cycling in treated fields.