Date of Award:

5-2020

Document Type:

Thesis

Degree Name:

Master of Science (MS)

Department:

Biology

Advisor/Chair:

Ricardo A. Ramirez

Co-Advisor/Chair:

Noelle Beckman

Third Advisor:

Erik Wenninger

Abstract

The clover root curculio (CRC) is an important forage pest throughout North America. Extensive larval feeding on host roots has been associated with reduced stand establishment, disruption of nutrient and water uptake, increased secondary plant pathogen infection, decreased winter plant survival, and reductions in forage quality and yield. Due to the hidden nature of larvae in the soil, CRC is often overlooked and integrated pest management programs are limited as there is a lack of management options. First, I surveyed northern Utah alfalfa for CRC natural enemies, particularly insect-attacking nematodes and fungi (entomopathogens) that could be used in biological control programs against CRC larvae. I found Beauveria spp. fungi most commonly infecting CRC larvae belowground. Next, I used recent information on the CRC life cycle in the Intermountain West to test multiple field applications of soil-active biological insecticides (entomopathogenic nematodes, fungi, and bacteria) and a synthetic systemic insecticide, flupyradifurone. Although these insecticides were compatible with spray equipment and alfalfa production, applications of these products did not reduce CRC larval populations or root damage in my studies. Further, the two application timings tested (before larval peak and during larval peak) did not increase application effectiveness. However, evaluating CRC suppression in the field was challenging because they are hidden in the soil, have patchy distributions, and were observed in low numbers. Lastly, I tested existing root-pathogen resistant alfalfa varieties for potential cross-resistance to CRC, and evaluated alfalfa currently being bred at Cornell University for specific resistance to CRC larvae. Although commercial root-pathogen resistant alfalfa had no effect on CRC, the CRC-resistant alfalfa developed at Cornell University may alleviate the impact of CRC larval damage through increased nodule production. This research provides the groundwork for finding effective and long-term management solutions for CRC in the Intermountain West and will assist in the continued development of insecticide application programs and resistant host plants to ultimately improve alfalfa production.

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