Effects of Organic Fertilizers on Herbivore Performance

Phoebe Scharle, Dr. Amanda Meier, and Dr. Bill Snyder Microbiology and Entomology, University of Georgia 101 Herty Drive Athens, Georgia 30602-6113

Plant-herbivore interactions are shaped by both soil nutrient availability and soil microbial communities. For example, soil microbes can upregulate plant defenses, reducing herbivore performance. Farmers add organic amendments to soils, altering macro-and micro-nutrients available to plants and soil microbial communities, with potential consequences for plant-herbivore interactions. Indeed, crops grown in soils with high organic matter and rich microbial activity often have a reduced prevalence of insect pests. However, we lack an understanding of how particular soil amendments, by altering soil nutrient availability and microbial communities, influence plant-herbivore interactions. Therefore, we evaluated how different organic amendments shape herbivores' abundances in the field. We examined this through a field experiment in tomatoes (Solanum lycopersicum) over the course of fourteen weeks. In a full factorial design, we fertilized four varieties of tomatoes (Cherokee Purple, Eva Purple Ball, Mountain Magic, Defiant PhR) with either chicken meal, fish meal, worm castings, a mix of all three, or nothing, and surveyed insect abundances biweekly. Over the season, hornworm caterpillars (Manduca sexta) were most abundant on plants of all varieties fertilized with chicken meal, and were most abundant on Cherokee Purple plants, consistently among fertilizer treatments. Armyworms (Spodoptera spp.) were also most abundant on Cherokee Purple plants but displayed no preference for fertilizer treatments. In contrast, flea beetles were most abundant on plants fertilized with fish meal, especially Defiant PhR plants. Our findings demonstrate that soil amendments, by altering plant quality, have strong effects on herbivore abundances in the field, but that the effects are herbivore species-specific.

Additional Abstract Information

Presenter: Phoebe Scharle

Institution: University of Georgia

Type: Poster

Subject: Ecology

Status: Approved

Time and Location

Session: Poster 5
Date/Time: Tue 12:30pm-1:30pm
Session Number: 4108