Ecological trade-offs associated with insecticide use, from Pennsylvania to Bangladesh

Open Access
- Author:
- Douglas, Margaret Rose
- Graduate Program:
- Entomology
- Degree:
- Doctor of Philosophy
- Document Type:
- Dissertation
- Date of Defense:
- May 23, 2016
- Committee Members:
- John Tooker, Dissertation Advisor/Co-Advisor
John Tooker, Committee Chair/Co-Chair
Mary Barbercheck, Committee Member
Christopher Mullin, Committee Member
Armen Kemanian, Outside Member - Keywords:
- predation
biological control
neonicotinoid
slug
ecosystem services
Bangladesh
Lablab purpureus
Zea mays
Glycine max
Deroceras
agroecology - Abstract:
- Integrated Pest Management (IPM) requires an understanding of the interaction between chemical and biological control tactics. In recent decades, seed treatment with neonicotinoids has become increasingly widespread in field crop production, but the full ecological and agronomic effects of these insecticides are still far from understood. This dissertation helps to fill this knowledge gap by describing the use of neonicotinoid seed treatments in U.S. agriculture, and examining the influence of these insecticides on pest and predatory invertebrates. In Chapter 1, I synthesized data from various government sources and pesticide use labels to estimate the national use of seed-applied neonicotinoids in the United States. In Chapters 2 and 3, I used laboratory and field studies together with insecticide residue testing to explore the movement of seed-applied neonicotinoids through a crop-slug-beetle food chain and its agronomic consequences in Pennsylvania no-till soybean and corn systems. I found that seed-applied neonicotinoids variably disrupt biological control of non-target pest slugs. Furthermore, field-collected slugs, earthworms, and caterpillars contained concentrations of neonicotinoids likely to harm predatory arthropods that consume them. In Chapter 4, I tested the generality of the effects of neonicotinoid seed treatments on arthropod natural enemies through a meta-analysis of field studies. By assembling almost 1,000 observations from North American and European experiments, I found that seed-applied neonicotinoids have a negative effect on insect natural enemies corresponding to a roughly 16% seasonal reduction in abundance. Taken together, my results shed light on the agro-ecological effects of neonicotinoid seed treatments and inform their targeted use. Finally, Chapter 5 comprised the international component of my dissertation. In a lablab bean production system in Bangladesh, I tested the hypothesis that biorational pesticides can replace broad-spectrum synthetic insecticides in insect pest management. Additionally, I used DNA barcoding to characterize emerging thrips pests and determine whether they need to be incorporated into lablab bean IPM programs. Biorational pesticides were variably effective against lablab bean insect pests, and my preliminary evidence suggests that flower thrips (mainly Megalurothrips spp.) pose a significant threat to lablab bean production and should be included in insect control efforts in this crop.