Understanding the Spatiotemporal Abundance of Soybean Gall Midge in Soil of Infested Soybean Fields

Authors

• Mikaelison da Silva Lima, University of Nebraska-LincolnFollow

First Advisor

Anthony Justin McMechan

Committee Members

Julie Peterson, Robert Wright, Thomas Hunt

Date of this Version

5-2023

Document Type

Thesis

Citation

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 Anthony Justin McMechan

Lincoln, Nebraska, May 2023

Comments

Copyright © 2023, Mikaelison da Silva Lima. Used by permission

Abstract

Soybean gall midge, Resseliella maxima Gagné (Diptera: Cecidomyiidae), was identified in 2019 after injury was reported in soybean in four midwestern U.S. states. Heavy infestations have the potential to result in the total loss of yield in the first 30 meters near the field edge. Larvae feed under the plant epidermis after hatching from eggs laid in natural openings near the base of the plant stem. This feeding causes dark discolorations and necrosis of the affected areas. After feeding the larvae leave the plant to form a cocoon and pupate in the soil. Adults can emerge in the same season or the following year. Despite the severity and damage caused by soybean gall midge attacks, there is very few management tactics available due to knowledge gaps.

To address knowledge gaps in soybean gall midge biology, a three-year field study was conducted to investigate the distribution of overwintering cocoons in the soil profile. Undisturbed soil cores (12 cm deep) were collected from four infested fields in 2019, 2021, and 2022. Cores were divided into two cm layers and processed individually using the brine flotation technique to separate cocoons from the soil with subsequent soybean gall midge counting. Results showed the greatest abundance of immatures (96.2%) was in the first six cm of soil depth. The majority (75.5%) of those were in the top two centimeters.

A second two-year field study was conducted in two soybean fields in eastern Nebraska to evaluate the abundance of soybean gall midge in the soil throughout the 2021 and 2022 growing season. Soil samples were collected at 4-11-day intervals and processed using a brine flotation technique to separate cocoons from the soil. The results showed that soybean gall midge population in the soil varied between fields and during each growing season. A significant interaction between field and time was identified in both years. In 2021, the first peak occurred in mid-July at both the Davey and Memphis sites. In 2022, first detections were similar at Memphis and Walton locations; however, the peaks did not always occur in the two fields in the same week. Soybean gall midge was almost undetectable in late-June and early-July in 2022. Abundance increased significantly early in August and maintained until mid-September in both fields in 2022.

These studies were the first to examine the spatiotemporal dynamics of soybean gall midge in the soil in infested fields. The findings are crucial for understanding the biology of soybean gall midge overwintering cocoons in the soil as well as the seasonal dynamics of this pest during the growing season. This knowledge informs future studies and guides development and application of management practices, such as tillage to disturb its biology and cycles of reinfestation in subsequent seasons to mitigate its damage to soybean.

Advisor: Anthony Justin McMechan