Project Details:

Soybean Gall Midge: Surveying the North Central Region, Adult Monitoring and Host Plant Resistance

Parent Project: Soybean Gall Midge: Identifying management opportunities for an emerging pest of soybeans
Checkoff Organization:North Central Soybean Research Program
Categories:Insects and pests
Organization Project Code:0327-020
Project Year:2021
Lead Principal Investigator:Justin McMechan (University of Nebraska)
Co-Principal Investigators:
Keywords: soybean gall midge

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

1) Determine the distribution and severity of soybean gall midge across the north-central region.
The goal of this study is to document the current distribution and relative damage of soybean gall midge in soybean across the north-central region. In 2018, researchers in Nebraska, South Dakota, Iowa, and Minnesota briefly documented the distribution of soybean gall midge in the four-state where significant damage occurred. Due to the rapid development of soybean gall midge as a significant pest of soybean, the distribution and damage of this pest were not documented using consistent methods. In addition, documentation of infested counties was primarily based on calls from stakeholders with only limited opportunities for systematic surveying of fields.
Sampling protocols for soybean gall midge have been divided into two categories depending on the historical occurrence of gall midge in an area. In states where soybean gall midge has not been found, researchers will actively engage stakeholders at field day and extension events to alert them about the pest. Postcards will be developed and distributed at these events to increase the likelihood of detection. Each state will utilize resources such as the department of agriculture, extension educators, and IPM scouts when it is applicable to check fields. With the exception of field reports, sampling soybean fields will begin at the R3 or early pod development and continue through R7 or beginning maturity. Conducting this survey during the mid- to late-reproductive stages of soybean will increase the likelihood of detection.
Researchers will target soybean fields adjacent to dense vegetation such as trees, shrubs or uncut grass. To assess a field, plants will be checked every 100 feet along a field edge (Fig. 6). Any plants along this transect showing early signs of death or wilting will be assessed for the presence of soybean gall midge larvae. Infestation by gall midge will be assessed on an individual plant by peeling back the outer tissue of darkened areas near the base of the plant. If larvae are found, they will be collected and stored in alcohol for species identification.
Areas with extensive damage and historical presence of soybean gall midge will be assessed by randomly selecting a soybean field every 5-10 miles on a transect through a county. In each field, samples will be taken at 1, 10, 20, 50, 100, and 400 feet from the field edge (Fig. 7). At each of these locations, 10 consecutive plants will be broken off at
ground level to determine if plants are infested. Each location will be scored as a proportion of plants infested at that location (6/10). For all sampling sites, the stage of development of soybean plants at the time of the sampling will be recorded. Documenting the distribution is critical for making stakeholders aware of the issue, directing future research efforts, and determining the ability of soybean gall midge to spread to other areas of the soybean growing region.

2) Determine the emergence timing and source of adult soybean gall midge.
Adult soybean gall midge emergence will be monitored using corn rootworm emergence cages. To determine the source for adult emergence, cages will be placed in soybean fields with signs of damage from the previous year, ditches adjacent to damaged fields (brome grass and other vegetation), and in the field being planted to soybean (Fig. 8). Monitoring will begin on April 1st and continue until adult populations cease to emerge. All current funding sources of adult soybean gall midge emergence data will end by the fall of 2019. This monitoring effort is the foundation for current management practices until other strategies can be established. A minimum of three cages will be used per site. Cages will be monitored every 2-4 days and adults will be collected and stored. After initial adult emergence, cages will be placed over infested soybean plants to determine the timing of emergence of the second generation. This coordinated multi-state effort will lay the framework for developing a model to estimate the timing of emergence for subsequent years. In the spring of 2019, a total of 24 emergence monitoring sites were established across Nebraska, Iowa, South Dakota, and Minnesota. With limited knowledge on soybean gall midge, farmers with significant historical damage can apply an insecticide as soon as possible following adult emergence. To facilitate communication on emergence, a rapid communication system was established through Blackboard connect to notify registered stakeholders via an automated phone call, text message, and email. As of October 31st, over 300 users have registered for the alert system. When an alert for the emergence of soybean gall adults is sent, stakeholders will be directed to the to get more information on the location to increase the potential efficacy of insecticide applications against the adult stage of soybean gall midge. These short-term tactics and notification system will greatly enhance control tactics against soybean gall midge and reduce the likelihood of excessive spraying at times when adults are not present or moving.

3) Screen soybean varieties for resistance or tolerance to soybean gall midge.
A total of 750 soybean lines representing the genetic diversity of the USDA Soybean Germplasm Collection in Maturity Groups I, II, III, and IV will be used for screening for plant resistance or tolerance to soybean gall midge. The soybean lines are landraces and improved cultivars collected from all areas of the world where soybeans originated or are grown. The diverse panel of lines already has DNA genotype information available in the 50K SNP data, and the selected lines are the same set used in current and previous NCSRP-funded research for the projects “Identifying high-yield genotypes in the USDA Soybean Germplasm Collection” (G. Graef et al., 2014-2016) and “Increasing the rate of genetic gain for yield in soybean breeding populations.” (L. McHale et al. 2016-2019). All 750 lines are being grown in a seed increase during 2019 to prepare for this experiment. Brief background and rationale for use of this set of lines is as follows: (1) About 90% of the current commercial soybean gene pool in the US is based on fewer than 17 soybean accessions; (2) There are nearly 20,000 unique soybean accessions in the USDA Soybean Germplasm Collection; (3) The diverse genetic types that exist in the collection have been a source of resistance genes for important soybean diseases and insect pests like phytophthora root rot, brown stem rot, soybean cyst nematode, Asian soybean aphid, and others, and may also possess genes for resistance to soybean gall midge; (4) The recent NCSRP-sponsored research with this set of 750 soybean lines used different scientific sampling methods to select diverse soybean genotypes from the collection, and we have shown that this set of lines represents the genetic diversity in the collection, particularly for maturity groups I, II, III, and IV.
For this study, the lines will be planted in three infested locations across the region: one field each in Nebraska, South Dakota and Iowa. The lines will be planted in single-row plots 5’ long, replicated four times in an incomplete block design. Locations for the variety trial will be next to areas of significant damage from gall midge in 2019. These sites will also coincide with locations that are monitored for adult soybean gall midge emergence as described in Objective 2 to evaluate whether or not a significant population was present. A susceptible commercial soybean line will be interspersed through the trial to determine if adequate soybean gall midge pressure occurred in the trial Each line will be evaluated for the presence of soybean gall midge damage and/or larvae approximately three to four weeks after adult emergence. Any soybean lines exhibiting damage across reps and locations will be considered susceptible and will be removed from the second year of testing. If sufficient variation in plant reaction to soybean gall midge is observed among the 750 lines evaluated in Year 1, we will be able to conduct a genome-wide association analysis using the insect reaction data and the genotype data of each line to identify genomic regions that are associated with that reaction (i.e., resistance). The same process will be repeated in 2021 with the lines that showed no signs of damage, or some kind of limited damage or resistance the previous year. Testing in the greenhouse on a subset of lines will also begin in 2020 with a minimum of three replicates per line. A susceptible commercial check variety will be run at the same time as experimental lines to determine host susceptibility. Soybean lines advancing to year three would be planted at all three locations to evaluate for damage and determine each line's yield potential. To determine yield, plot size will be increased to four rows wide, and all data collected on the center two rows of a bordered plot.

4) Disseminate information to stakeholders on current information and management for soybean gall midge.
Sixteen of the Co-PIs have extension appointments and are well suited for communicating details about soybean gall midge biology and management recommendations. During Years 1 and 2, we will create short summaries (e.g., 2-4 page publications) from our multi-state objectives 1-3 and disseminate findings to stakeholders. During Year 3, we will create a pocket-sized field guide that includes data generated from this project and other companion projects. Guides will be distributed to all participating Co-PI’s. Expected audiences include farmers, crop consultants, agribusiness, industry, and other extension personnel.

Project Objectives

1) Determine the distribution and severity of soybean gall midge across the north-central region.
2) Determine the emergence timing and source of adult soybean gall midge.
3) Screen soybean varieties for resistance or tolerance to soybean gall midge.
4) Disseminate information to stakeholder on current information and management for soybean gall midge.

Project Deliverables

? Provide a map of soybean gall midge distributions and its damage to soybean in the north- central region.
? Increase awareness of soybean gall midge and reduce the likelihood for unexpected losses.
? Create platform to share current research on soybean gall midge with researchers and stakeholders across the region.
? Mobilize resource and direct efforts in areas with pressure or presence of soybean gall midge.
? Provide stakeholders with resource to make management decision on soybean gall midge
? Increase return on investment of short-term control strategies (i.e. insecticides)
? Develop adult soybean gall emergence model to aid in making future management decisions
? Identify any soybean genotypes or lines with resistance or tolerance to soybean gall midge.
? Map genomic regions in soybean associated with reaction to soybean gall midge.
? Potentially identify putative resistance genes.
? Depending on the level of resistance, preliminary information on yield of lines under significant insect pressure vs. non-infested yield levels will be obtained.
? Disseminate information on resistance/susceptibility reaction and mapped genomic regions so public and commercial breeding programs can screen their germplasm for alleles that confer resistance to soybean gall midge, and use that information to facilitate more rapid identification and development of elite, resistant soybean cultivars
? Understand if/what follow-up is needed to fully characterize reaction to soybean gall midge
? Increase stakeholder awareness and understanding of soybean gall midge through publications and field guides
? Engage and maintain dialogue with stakeholders to identify barriers to adoption or implementation of management recommendations for soybean gall midge

Progress of Work

Updated March 31, 2021:

Soybean Gall Midge Survey
The majority of the states were able to participate in determining the distribution and severity of soybean gall midge in 2020; however, a few states (Michigan, Ohio, and Indiana) were unable to participate. As a result, Michigan and Ohio have redirected their efforts by producing an informational soybean gall midge postcard which will be sent to approximately 72,000 soybean farmers that will be printed and mailed in April. Nebraska, Iowa, South Dakota, and Minnesota plan to conduct field surveys on the distribution and severity of soybean gall midge during the 2021 season. Iowa plans to make a significant effort east of its current distribution to follow up on the impact of the Derecho from the August of 2020.

Adult Emergence Timing and Source
Planning is almost complete for the objective to determine the emergence timing and source of adult soybean gall midge for the 2021 season. Nebraska has secured cooperation with soybean farmers with 14 sites in east-central Nebraska across Otoe, Lancaster, Cass, Sarpy, Saunders, and Butler counties to track the emergence of adults. Eight of those sites will have research plots on seed treatments, granular at-plant, and foliar insecticides, as well as cultural, genetic, and biology-related studies. Northeast Nebraska has five sites planned in Cedar, Wayne, and Stanton counties. Iowa plans to have at least two sites in O’Brien and Cass Counties. Minnesota will have at least two emergence monitoring sites in Rock county with an additional site in Yellow Medicine County. Planning for sites is still underway in South Dakota. In Nebraska, emergence sites will be paired with soil collections through the USDA CPPM grant to determine if the presence of silken cocoons are correlated with adult emergence from overwintering sites. Minnesota and Iowa will collect soil samples to support this effort.

Germplasm Screen
Packaging and coordinating the field screen of the U.S. germplasm for soybean gall midge is well underway, with two sites being conducted in east-central Nebraska and a single site in Iowa and South Dakota. The complete set of accession lines (768) tested in 2020 will be repeated in the 2021 season. A total of three lines were uninfested across both sites in Nebraska and Iowa. A protocol was established in Nebraska for injury rating during the 2020 season and all three states have agreed to use that procedure in 2021. Adding an injury scoring system will allow for the screening of potential tolerant lines for soybean gall midge. Limitation from Covid-19 set back the potential for a GWAS analysis due to a reduced data set. It is anticipated that this will be back on track at the end of the 2021 season. Small changes were made to the trial design by blocking maturity groups together to allow for a more uniform evaluation during the season.

Extension Efforts
Significant efforts were made to disseminate information to clientele despite the limitations of Covid-19. The website was established with over 2,200 unique visitors during the 2020 growing season. Daily maps were generated, and maps are already being established for adult monitoring sites for the 2021 season. A specific tab was created on the page for clientele to track the identification of new counties that may be confirmed during this growing season. A three-part multi-state webinar series on soybean gall midge was successfully conducted during January with 393 registrants. Video recording of the webinars are available on the website. The number of views of these recordings will be reported at the end of 2021. Of the participant that filled out the survey, 95%, 97%, and 97.5% were satisfied or very satisfied with the sessions on soybean gall midge identification, biology, and management, respectively. Nebraska recently completed a NebGuide on Soybean Gall Midge, which is expected to be available within the next month. This NebGuide will be updated to fit the regional understanding of soybean gall midge this year. In addition, North Dakota and Missouri coordinated with PD McMechan to produce fact sheets for their respective states. Dr. Erin Hodgson with Iowa State has also started a design for extension products that will be handed out at field days later this season. Presentations on soybean gall midge work that was funded by NCSRP and USB were given in Nebraska, Iowa, Minnesota, South Dakota, Missouri, Wisconsin, Indiana, and Illinois over the past couple of months. Research from this project was also presented to the S1080 Soybean Entomologist group that spans almost the entire soybean-growing region within the United States. The number of clientele that views these presentations is not clear as some of the presentations were recorded.

Final Project Results

Benefit to Soybean Farmers

Field surveys provide soybean farmers with an estimation of the level of risk for injury in their area. Newly identified areas provide an opportunity to engage farmers and their retailers to make them aware of the pest and the potential resources to manage it. Large widespread wind events like the derecho in the midwest 2020 provide strong justification to the value of scouting fields for this new species and determining its distribution.

Soybean growers in areas already infested with soybean gall midge can take advantage of the alert network by implementing border spray applications, tillage treatments, and mowing vegetation around the field in an effort to mitigate losses. Preliminary management practices have focused almost exclusively on insecticides to mitigate pest pressure. The efficacy of these products and the window of opportunity to apply them is largely unknown. In addition, relying on pesticides as a pest management program may lead to secondary pest issues or resistance to insecticides by soybean gall midge.

To date, no commercial soybean varieties have been identified as resistant to soybean gall midge. Roundtable discussions found that a number of stakeholders suspected a particular variety had resistance but such situations were likely a result of other factors since the same soybean variety was found to be susceptible at another location. Evaluating soybean lines for resistance is an essential component of a pest management program. A successful screening process would greatly reduce the number of insecticide applications, limiting issues with secondary pests and soybean gall midge developing insecticidal resistance.

Extension is a critical method for delivering information to soybean farmers. An online soybean gall midge series is the planning stage for early 2021. Such events provide farmers with up-to-date information and a chance to express their concerns and weigh in on future research as well as partner with research entomologists.

Performance Metrics

? Incorporate map into extension publications.
? Complete field survey of states that could not participate in 2020.
? Contact growers to coordinate sites for monitoring.
? Place and monitor cages for emergence of soybean gall midge.
? Deploy temperature sensors at selected sites.
? Begin refining model for determining emergence of soybean gall midge.
? Identify sites for study.
? Plant sites and monitor for soybean gall midge infestation.
? Complete second field screening for resistant lines.
? Conduct greenhouse study on lines that show resistance under field conditions.
? Run GWAS on two years of data.
? Conduct field days and give presentations to stakeholders on current research on soybean gall midge.
? Develop short summaries on current research projects to provide to stakeholders.
? Provide alert system on soybean gall midge.

Project Years