Entomology, Department of


First Advisor

Anthony Justin McMechan

Date of this Version

Spring 2022


Montenegro, V.M. Soybean gall midge (Resseliella maxima Gagné): Insecticide efficacy and seasonal larval abundance. M.S. thesis, University of Nebraska-Lincoln.


A THESIS Presented to the Faculty of The Graduate College at the University of Nebraska In Partial Fulfillment of Requirements For the Degree of Master of Science, Major: Entomology, Under the Supervision of Professor Justin McMechan. Lincoln, Nebraska: February 2022

Copyright © 2022 Vilma María Montenegro Castro


Soybean gall midge, Resseliella maxima Gagné was recently identified as a new species injuring soybean in Nebraska, Iowa, South Dakota, Minnesota, and Missouri. Resseliella maxima injury is caused by its three instars that feed on tissues within the soybean stem. Infested plants exhibit a darkening of the stem, disrupting nutrient flow within the plant and can lead to wilting or death of plants. Total yield losses can occur in the first 30 m of the field in heavily infested sites. The biology and behavior of this newly described insects is not well understood and management strategies for the management of this pest are needed.

A field study was conducted to evaluate the efficacy of different insecticide classes to control R. maxima. This study was conducted in one location in Nebraska in 2020 and 2021. Treatments were arranged as a randomized complete block design with four replications. Single applications were evaluated at different timings based on overwintering emergence, at 0, 5 and 10 days after the first adult detection occurred. The efficacy of insecticides was evaluated by the proportion of infested plants, number of larvae, plant injury, and final yield. Overall, no treatment showed consistent control of R. maxima in the field.

The second study focused on the seasonal larval abundance of R. maxima in the field. The objective of this study was to determine the abundance of R. maxima larvae on soybean plants from overwintering adult emergence until harvest. Plants were collected from two field locations each year in eastern Nebraska in 2020 and 2021. Stems were dissected, and the number of larvae were separated into two categories (white and pigmented) and counted. Larvae were present in the field from mid-June until late August or September, with the greatest number of larvae being observed from late July to early August.

Both studies are the first to explore a) insecticides applied at different timings to control R. maxima in the field, and b) the seasonal larval abundance of R. maxima in the field. The results of these studies provide information that can be used to identify possible strategies for the management of R. maxima. In addition, the studies provide insights into the biology and ecology of this recently described pest.

Advisor: Anthony Justin McMechan