Graduate Studies, UNL

 

Dissertations and Doctoral Documents, University of Nebraska-Lincoln, 2023–

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First Advisor

Julie Peterson

Second Advisor

Ana Vélez Arango

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

Greg Kruger, Robert Wright

Department

Entomology

Date of this Version

5-4-2026

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College at the University of Nebraska in partial fulfillment of requirements for the degree Doctor of Philosophy

Major: Entomology

Under the supervision of Professors Julie Peterson and Ana Vélez Arango

Lincoln, Nebraska, May 2026

Comments

Copyright 2026, Andrea Rilakovic. Used by permission

Abstract

Western bean cutworm, Striacosta albicosta (Smith), is a univoltine moth in North America, recognized as an economic threat to both corn (Zea mays L.) and dry bean (Phaseolus vulgaris L.). In the Midwest of the United States, S. albicosta can cause severe damage by reducing the quantity and quality of corn ears through larval feeding. Currently, options for Bacillus thuringiensis (Bt) proteins that can effectively control S. albicosta are limited, relying on only one Vip3A effective protein, while other growers use insecticide application via airplanes or center pivot irrigation systems, known as chemigation. Given the importance of chemical applications for S. albicosta, the second chapter of this dissertation focused on identifying factors influencing decision-making regarding S. albicosta insecticide management in Nebraska through a stakeholders' survey. As a result, quantitative data were provided, and we were able to identify factors associated with successful or unsuccessful insecticide applications via both application methods. In chapter three, a two-year field study was conducted to evaluate the efficacy of chlorantraniliprole (diamide) and bifenthrin (pyrethroid) via chemigation. Chlorantraniliprole and bifenthrin insecticides were applied at the minimum and maximum label rates using two application depths (6.35 mm and 19.05 mm). Chlorantraniliprole provided better control of S. albicosta larvae than bifenthrin. Application depths of the applied insecticides did not influence ear feeding injury performed at 28 days after treatment (DAT). This work addresses a critical gap in chemigation efficacy that has remained unexamined for over four decades. In chapter four, we performed aerial and chemigation applications under laboratory conditions using parameters collected from the field for commercial insecticide applications recommended for S. albicosta control in corn. Chlorantraniliprole and bifenthrin were applied at the highest and lowest label rates. The simulated aerial application was more effective than simulated chemigation in controlling S. albicosta, resulting in 100% mortality 24 h after infestation. Within the chemigation applications, chlorantraniliprole treatments were effective at both rates for all instars, while the high rate of bifenthrin exhibited greater efficacy than the lower rate. In chapter five, we conducted an on-farm research study over two growing seasons to evaluate the efficacy of chlorantraniliprole and bifenthrin for managing S. albicosta in corn using aerial and chemigation applications. In addition to efficacy data, we quantified spray characteristics, including coverage, deposition, droplet canopy penetration, and insecticide residue on corn leaves. In the field, chlorantraniliprole resulted in the lowest ear-feeding injury compared to control 28 DAT. There was no difference in ear feeding injury or yield between application methods. Aerial application deposition, spray coverage, and insecticide residues were greater on tassels than on ear leaves within the corn canopy. Out of the total spray volume applied aerially, only 36.4% reached the tassel level, whereas 19.8% reached the ear zone. Data generated in this research may help refine current and future insecticide application guidelines, not only for S. albicosta but also for other ear-feeding pests in corn.

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