Graduate Studies, UNL

 

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

First Advisor

Anthony Justin McMechan

Degree Name

Doctor of Philosophy (Ph.D.)

Committee Members

Ana Maria Vélez, Erin Hodgson, Joe Louis, Nicolas Cafaro

Department

Entomology

Date of this Version

2025

Document Type

Dissertation

Citation

A dissertation presented to the faculty of the Graduate College of the University of Nebraska in partial fulfillment of requirements for the degree Doctor of Philosophy (Ph.D.)

Major: Entomology

Under the supervision of Professor

Lincoln, Nebraska, December 2025

Comments

Copyright 2025, the author. Used by permission

Abstract

Resseliella maxima Gagné (Diptera: Cecidomyiidae) is a recently described and economically significant pest of soybean (Glycine max (L.) Merr.) in the Midwestern United States. Since its identification in 2019, this species has become widespread and is now associated with substantial yield losses in parts of the region. Prior to its formal description, orange larvae were observed in soybean associated with plants damaged by hail, suggesting that plant injury may influence infestation. Given the pest’s economic importance, understanding the role of hail injury and developing effective, integrated management strategies are critical for mitigating its impact.

Field studies were conducted to evaluate cultural and chemical management strategies for R. maxima. In 2021, a study was conducted at four locations in eastern Nebraska to assess three soybean planting dates with and without an at-plant insecticide (phorate). A second study, conducted in 2021 and 2023 at one site each, evaluated five planting dates with and without an imidacloprid seed treatment. For both studies, the proportion of infestation, larval number, plant injury, and grain yield were collected. Results showed that planting dates influenced R. maxima abundance and plant injury, however, insecticide treatments varied among locations and planting dates.

To better understand imidacloprid seed treatment efficacy, a novel bioassay was developed to establish baseline susceptibility for R. maxima pigmented larvae. Nine insecticide concentrations and a control were tested on two larval populations. Mortality was recorded after 24 and 48 hours to estimate LC50. The results demonstrated that this method is suitable for assessing R. maxima susceptibility to imidacloprid and other insecticides for potential use in resistance monitoring and management programs.

Field studies in 2022 and 2023 in eastern Nebraska evaluated the impact of hail injury in soybean on R. maxima larval abundance. A simulated hail machine was used to create plant injury at three soybean growth stages, and stem injury categories were developed to assess injury severity. Results indicated that severe hail injury increased R. maxima infestation and larval abundance.

Advisor: Anthony Justin McMechan

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