Project Details:

Title:
Soybean Entomology in the North Central Region: Management and outreach for New and Existing Pests (2017)

Parent Project: Soybean entomology in the North Central region: Management and outreach for new and existing pests
Checkoff Organization:North Central Soybean Research Program
Categories:Insects and pests, Nematodes
Organization Project Code:NCSRP
Project Year:2017
Lead Principal Investigator:Kelley Tilmon (The Ohio State University)
Co-Principal Investigators:
Punya Nachappa (Indiana University)
Erin Hodgson (Iowa State University)
Matthew O'Neal (Iowa State University)
Brian McCornack (Kansas State University)
Janet Knodel (North Dakota State University)
Deirdre Prischmann-Voldseth (North Dakota State University)
Robert Koch (Northwest Research and Outreach Center, University of Minnesota)
Christian Krupke (Purdue University)
Adam Varenhorst (South Dakota State University)
Andy Michel (The Ohio State University)
Brian Diers (University of Illinois at Urbana-Champaign)
George Heimpel (University of Minnesota)
Bruce Potter (University of Minnesota)
Deborah Finke (University of Missouri)
Thomas E Hunt (University of Nebraska)
Robert Wright (University of Nebraska)
Glen Hartman (USDA/ARS-University of Illinois)
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Keywords: stink bugs, pollinators, aphids, IPM, pesticide resistance, resistant varieties, breeding, outreach

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

The subject of this proposal is research and outreach on soybean entomology in the North Central
Region. The program areas in this proposal encompass extension and outreach of project results,
insect monitoring and management for new and emerging insect pests in the region, aphidresistant
varieties and virulent aphid biotypes, and biological control. Projects within these
program areas include the creation and distribution of extension deliverables, stink bug monitoring
and management, studies on the ability of pollinators to increase yield potential, monitoring for
soybean aphid insecticide resistance, breeding for aphid-resistant varieties, genotyping and
mapping virulent aphid biotypes that overcome resistant varieties, developing virulence
management strategies, and the determining economic return on resistant varieties. These
priorities for soybean entomology were determined through a needs-assessment process in 2014
and early 2015. We obtained and compiled feedback from a focus group and survey of producers,
industry personnel, and other stakeholders, focus groups with soybean entomology research and
extension faculty, and discussions with soybean checkoff boards, in order to identify and address
the top entomological needs in the region.
Our interdisciplinary entomology and plant breeding team, comprised of 18 research and
extension scientists in 12 states, has a long history of working together to solve insect problems of
regional importance in soybean. This proposal builds on many of our past NCSRP-funded
projects and results. Our past work has demonstrated the utility of aphid-resistant varieties in
soybean pest management and greatly advanced the state of plant breeding for these varieties,
validated the economic superiority of scouting and foliar insecticides compared to insecticidal
seed treatments, supplied critical basic information on aphid biotypes that can overcome resistant
varieties, and has significantly advanced the state of importation biological control for soybean
aphid. In addition, we have a strong track record of providing tangible, user-friendly outreach
products to ensure that research generated from our project is available to producers in a form they
can use.
Though in the past our efforts have been focused on soybean aphid, there are several new or
emerging pests of soybean in the North Central Region which deserve attention. For example,
economically damaging populations of native stink bugs are becoming more common in several
states, and the introduced brown marmorated stink bug is spreading rapidly in the Midwest (in
Ohio, where it has been in the North Central region the longest, some locations have experienced
up to 30% yield loss from this pest). Another insect, thrips, that have always been present in
soybean at low levels have new damage potential as vectors of soybean vein necrosis virus. While
a massive research effort on such new and emerging pests is not yet practical, we are well poised
for background work that will (1) diagnose the extent of current problems, and (2) position us well
to respond to increasing problems in the future, by doing the background work necessary for
management recommendations. Another important area for entomological research in soybean is
on pollinators. There is increasing evidence that soybean yield increases when plants are visited
2
by pollinators, despite being bred for self-fertilization. This improvement varies between 6% to
18% depending upon type of pollinators present. Research in this proposal addresses the yieldincrease
potential from these beneficial insects. Other objectives relate to aphid resistant varieties,
how to make this resistance durable and sustainable, and how they may fit economically into
soybean production systems.

Project Objectives

Project Deliverables

Progress of Work

Update:
I. Extension and Outreach
We wrote 5 journal publications and gave 69 extension and scientific presentations. The publication on stink bugs of the North Central Region is in final editing. Progress towards publication has been delayed by the 3-month maternity leave of the outreach coordinator responsible for the guide.

II. Insect Monitoring and Management
1. Stink bug monitoring and management: Participants sampled stink bugs in a total of 59 fields last summer, to develop recommendations tailored to the region. We devised a preliminary sampling plans for field edges and interiors, which will be refined by a repeat of the study.

2. Pollinator diversity and soybean yield: Participants in ND, SD, IA, OH, MN, NE, IN, MO, WI collected pollinators in soybean fields last summer. Samples processing/ID by ND is 75% complete.

3. Soybean aphid insecticide resistance: We are working on a DIY assay kit to test aphids for resistance to thiamethoxam insecticide. Optimizations to the kit include more specific instructions on handling and classifying aphids, inclusion of a video demonstrating aphid handling technique, and a discriminating dose in the kits to reduce variability and sources of error.

4. Monitoring for aphids, thrips, and soybean vein necrosis: Soybean vein necrosis virus is transmitted by thrips. We sampled thrips from suction traps in 6 states. We identified thrips samples (still in progress). In IN, IL, IA thrips populations started to rise in June, but later in northern states. Populations of thrips vectors of SVNV are high during August in Iowa and Indiana which coincides with appearance of the disease in these states (primetime for monitoring). We are preparing the the suction trap network for summer.

5. Technology development: The goal is to develop an aphid-counting app. Images collected during the summer of 2016 are still being counted and cataloged. The Windows application is now able to automatically cut out all backgrounds from imported images, which leaves just the leaflet with aphids to scan. This reduces processing time and false positives, which will provide the user with quicker aphid counts.

III. Resistant Varieties and Biotypes

1. Breeding for resistant varieties: The Diers program is developing and releasing soybean varieties with aphid resistance. The backcrossing of the aphid resistance genes Rag4 and Rag6 into Rag1,2,3 cultivars is continuing. Rag4 backcrossing is complete and this summer we will select plants with all combination of Rag1-4. The backcrossing will continue this summer and into next year until we have sets of lines developed with all combinations of Rag1-4 and Rag6. The University of Illinois is commercializing 4 varieties with Rag2, 1 with Rag1 and 3 with Rag1+2. In 2013, we showed that the resistance gene Rag2 was associated with reduced yield. We have followed that research with a study to determine whether the reduced yield was the result of linkage between Rag2 and a second yield reducing gene or because the resistance gene directly reduced yield (pleiotropy). This research was just completed and we found that the yield reduction was the result of a second yield reducing gene and breaking the linkage between these genes should not be very difficult.

2. Aphid virulence genotyping and mapping: Our goal is to map aphid virulence. We are phenotyping the F1 reciprocal crosses of soybean aphid biotypes 1 and 4 (in progress). This will determine the virulence of these F1 types on soybean breeding lines with Rag1, Rag2, Rag1 + Rag2, and checks. A preliminary linkage map has been created from the biotype 1 and biotype 2 cross. A major QTL was detected on linkage group 2, but more data is necessary to confirm.

3. Aphid virulence management for resistant varieties: Modeling is ongoing. We are adding parasitoids to the microcosms to see how that may influence virulence management. In 2017 we will focus on how integrated refuge fields (resistant plants with a small percentage of susceptible plants), impact immigration into fields.

4. Economic returns on resistant varieties: This is a three-summer study designed to assess the economic returns on herbicide tolerant and aphid resistant traits. Preliminary results are that there were significant differences in yield between treatments at both locations. In general, the early-planted treatments had higher yield than late-planted treatments. There were also significant differences among varieties, but an inconsistent pattern between early- and late-planted treatments.


IV. Biological Control
We analyzed data to see impact of thiamethoxam seed treatments on parasitoids: it appears not to affect them. We conducted 3 overwintering experiments for soybean aphid parasitoids; emergence will be measured this spring. Dissections of a subsample of these mummies indicated that most A. certus and A. glycinis survived the winter while most A. rhamni had not.

View uploaded report PDF file

Update:
I. Extension and Outreach

We wrote 7 journal publications and gave four scientific talks based on our data. The majority of extension presentations will be given in the next reporting period which covers winter meetings. Final editing has been completed for the publication on stink bugs of the North Central Region, and we are negotiating with printers. We anticipate copies will be available for distribution during the winter extension season, and a pdf will be available for free distribution at SRII and other online sites.


II. Insect Monitoring and Management

1. Stink bug monitoring and management: This is the second year of a 3-year study. The goal is to devise management thresholds for stink bugs that are specific to the North Central Region. In 2017, Michigan was added to the project, resulting in a total of 9 states. The methodology for data collection was similar to that used in 2016. Each state selected for 2 sites and 4 fields per site. Fields were sampled on a weekly basis using sweep-net sampling, starting at beginning-pod (R3) growth stage to beginning-maturity (R7) growth stage. In each field, 4 sample units (1 sample unit=25 sweeps) were collected in the edge and 8 sample units were performed in the interior, resulting in a sample size of 12 sample units per field. Currently, some collaborators are still processing and sending the samples to the University of Minnesota. So far, samples from Minnesota, Indiana, Michigan and Nebraska were received and stink bugs species are being identified and data recorded.

2. Pollinator diversity and soybean yield: The goal of this study is to document the diversity of pollinators present in soybean fields. Pollinators may enhance soybean yield, and soybean may serve as an important reservoir for pollinator biodiversity. Participants in ND, SD, IA, OH, MN, NE, IN, MO, WI collected pollinators in soybean fields. Samples from all nine participating states were sent to North Dakota for sorting, sample preparation, and species identification (a highly skilled and detailed job). All samples have been processed. All specimens have been prepared and labeled, identification has begun. We anticipate completing sample identification this winter. Outputs will be produced in the beginning of Year 3 once the data set has been completed and analyzed. Results of the pollinator survey in soybean will be compiled into a PowerPoint for extension presentations, extension publication, scientific posters, PowerPoint for professional presentations, and a peer-reviewed publication. For the project to assess the Diurnal activity of wild and managed bees in soybeans: Currently the EPA requires farmers to limit their application of insecticide to periods when bees are not on flowers to reduce exposure. Honey bees (and other bees) typically fly only during periods of daylight, which limits applications to dusk. Some commercial applicators have questioned whether honey bees are active throughout the entire day or if they limit their foraging to optimal periods of activity, when temperatures are not at their highest. In order to gain a better understanding of this topic we conducted a study to determine the diurnal activity of honey bees and other bees in soybean fields growing in a variety of environments along a nationwide transect, from Mississippi to South Dakota. We located soybean farms in IA, SD, OH, and MS that had one or more honey bee colonies placed within 0.5km of the field. We used bee-bowl pan traps to measure bee activity in fields every 3 hours from 7am to 10pm. Sampling took place once a week from R1 to R4. These data are still being processed. In addition to understanding how bees use a field throughout the day we were also interested in whether or not the community of bees and activity density varied within the fields when compared to the grassy perimeter outside of fields. To examine this we placed bee-bowl transects in the field interior and grassy perimeter of 20 soybean fields in IA. We found no difference in the abundance of wild bees or honey bees in the two field locations. The results from these projects can help us to better understand how bees utilize agricultural fields and can more accurately inform the decisions being made for pollinator conservation and timings of insecticide applications.

3. Soybean aphid insecticide resistance: The goals of this objective are to monitor for soybean aphid resistance to the insecticide thiamethoxam in the North Central Region, and to develop a DIY assay kit to test aphids for resistance to thiamethoxam insecticide. Our resistance monitoring has detected shifts in tolerance in certain soybean aphids, but the shifts are very low. We have also fine-tuned the bioassays used to monitor this resistance with various improvements. The most recent improvement is verification that bioassays performed with mixed ages of aphids are reliable (which is important because this is more practical than age-synchronized monitoring). In addition, it was possible to incorporate growth rates measurements, which improves the assessment of population- level responses. With regard to development of the “do-it-yourself” kits, we have tried many methods to make this user-friendly for crop consultants. However, the soybean aphid has proven too delicate for the DIY kit approach unless the end-user is trained to handle these types of insects. Too much soybean aphid injury and mortality occurs during aphid transfer. However, we have developed the methodology to the point where it is a useful research tool for trained researchers involved in resistance monitoring. Instead of further effort to develop a kit for widespread use, we are shifting our focus to aphid genetics as a component of resistance monitoring. Dr. Andrew Michel’s Lab (Ohio) has been assisting with genetic typing and development of clonal lineages. One hundred-sixty clonal populations were sent to Nebraska and each population is undergoing requisite population increase needed for bioassay.

4. Monitoring for aphids, thrips, and soybean vein necrosis: Soybean vein necrosis virus is transmitted by thrips. We sampled thrips from suction traps in 6 states. We have completed thrips survey for the 2016 growing season and begun processing the 2017 samples. There does not appear to be much thrips activity in May in most of the locations. Thrips populations start to increase in June which coincides with early vegetative stages of soybean in most Midwest states. The northern states don’t seem to have high thrips numbers even in June. Thrips activity peaked in July-August in most states and begins a decline in September. Populations of thrips vectors of SVNV are high during July-August in most locations. This coincided with appearance of the disease in IN but we did not receive any SVNV samples from other states. Regarding suction trap monitoring for soybean aphid population trends, in 2017, the peak of soybean aphid collection was in the middle to the end of September. Meaning that there was not a notorious summer migration, but since the temperature was still ideal for soybean aphids’ rapid development, the fall migration was abundant especially in Indiana and Iowa. The suction traps from Chase, Louisiana had soybean aphids on September 2nd (2 specimens). Only a few aphids were collected in Manhattan, Kansas from September 8 until middle of October, and none from Columbia, Missouri. Other aphid species of agricultural interest included the capture of cereal aphids including the bird cherry-oat aphid (Rhopalosiphum padi, significantly high in Iowa, Kansas and Missouri), and English grain aphid (Sitobion avenae, present mainly in Iowa, Minnesota, Kansas and Missouri). New records of few specimens of the invasive species (sugarcane aphid, Melanaphis sacchari) were counted for SOYFACE (University of Illinois), SEPAC and NEPAC, and Kellogg. For Chase, Louisiana the peak was the middle of August, and in Manhattan few sugarcane aphids were caught on September. The cotton-melon aphid, Aphis gossypii, was significantly present in some suction trap locations in Illinois, Indiana, Louisiana and Michigan. The black legume aphid (Aphis craccivora) and the spotted alfalfa aphid (Therioaphis trifoliate).

5. Technology development: The goal is to develop an aphid-counting app. We are currently approximately 70% done with processing images collected over the past two summers (approx. 3000 total). Currently, mobile device cameras equipped with the android operating system are able to detect more aphids on infested soybean leaflets compared to iOS-based devices when using our aphid counting software. Specifically, the Samsung galaxy S5 phone camera combined with a black or white background worked well with the aphid counting software and its utility in estimating changes in soybean densities is currently being assessed under greenhouse conditions. This past summer we conducted a preliminary greenhouse study to address carrying capacity questions that incorporates the use of the imaging software. Challenges to date include capturing pictures of aphids on newly developing soybean leaves at the terminal bud and aphids on stems; greenhouse trials this fall/winter will address this issue. We are also exploring other potential uses of the software for use in soybean aphid management. Algorithm parameters can be adjusted directly in the program, which allows the user to select the color and other detection features for a range of images. For example, the software can count the number of aphid cast skins because of their distinct color. There are several parasitized aphids in one of the datasets we have collected, and our plan is to see whether the software can distinguish these aphids from non-parasitized ones. This added utility might prove beneficial for extension efforts associated with the biological control objective.

III. Resistant Varieties and Biotypes

1. Breeding for resistant varieties: The Diers program is developing and releasing soybean varieties with aphid resistance. The backcrossing of the aphid resistance genes Rag4 and Rag6 into cultivars that already have Rag1, Rag2, and Rag3 is continuing. During the summer of 2017, we produced BC3F1 seed for Rag6 in both the MG I Titan background and the MG II LD02-4485 background. The BC3F1 seed is being planted in the greenhouse so that the fourth and final backcross can be conducted early this winter. For Rag4, we completed the backcrossing of this gene in both backgrounds and now this gene is being combined with Rag1-3. In the LD02-4485 background, crosses were made this summer between plants with Rag4 backcrossed into them and Rag1-3 backcross plants. F1 seed from these crosses will be planted in the greenhouse to develop populations segregating for all four genes. In the Titan background, populations of F2 plants segregating for Rag1-4 were grown in the field this past summer. This winter we will grow plants in a greenhouse from these populations to identify those plants with the resistance allele for all four genes. These plants will then be crossed to backcross plants with Rag6 to complete the stacking of all five genes. Breeding to develop new cultivars with Rag1, Rag2 and stacks of Rag1 and Rag2 is continuing. Experimental lines with different combinations of these resistance genes were yield tested in 2017 and we are awaiting the completion of harvest so results from these tests can be summarized and selections made. In addition, commercial production or commercial scale seed increases are occurring for one variety with Rag1 only, four varieties with Rag2 only, and two varieties with Rag1 and Rag2 stacked together. These varieties are being sold under the Illini Brand name or are being licensed to other companies for their branding.

2. Aphid virulence genotyping and mapping: Our goal is to map aphid virulence. Genetic mapping of virulence has revealed segregation distortion among B1 and B2 reciprocal crossed. In other words, the ratio of genotypes in the F1 generation is not what was expected. Some offspring of this cross appear to be either sterile or inviable. Survivors in the F1 generation appear similar to the female genotype regardless of biotype (i.e. female drive). Reasons for this phenomena include disparate genetic divergence between biotypes 1 and 2 (which has also been observed), or drastically different bacterial symbionts (which is currently being studied). We observed high migration to buckthorn this past autumn and have made collections. These samples will be genotyped and compared to aphids already collected from 2017. Populations include Iowa, Minnesota and Ohio. Aphids from the above collections will also be screened for phenotyping on Rag varieties. Based on the segregation distortion and female drive, we are comparing and genotyping Wolbachia from the soybean aphid. Wolbachia is a bacteria that can be found within insects that often induces mating incompatibilities. If indeed crosses of B1 and B2 are infertile, then the spread of virulence may be more rapid and place more emphasis on a refuge.

3. Aphid virulence management for resistant varieties: During the 2017 growing season we completed a field study in three states (Iowa, South Dakota, and Ohio) in quarter-acre, replicated plots to measure the impact of a Refuge-in-a-Bag approach to using aphid-resistant soybeans. This large scale allows us to robustly measure yield responses to both the different RIB options as well as insecticide use. In this experiment, we grew four options; 100% Susceptible; 100% Resistant; 90% Resistant and 10% Susceptible; 75% Resistant and 25% Susceptible. By mixing susceptible with resistant soybeans we can limit the build-up of virulent aphids that survive on the resistant soybeans. To determine if these options protected soybeans from the soybean aphids, each plot was split with one half kept aphid-free through use of a pyrethroid insecticide (i.e., Warrior); the other aphid was not sprayed with insecticide. At all states, aphid populations were assessed once a week and yield data will be taken at harvest (data not in yet). Preliminary data assessments from Iowa show two interesting finds. The first is that all options using the aphid resistant line, regardless of how much susceptible soybean was mixed in, had lower aphid populations than the plots with only aphid-susceptible soybeans. Second, two insecticide applications were required at the Iowa location, in part because the insecticide did not perform as expected. This location has experienced pyrethroid-resistant aphids. Going forward, yield data will help us determine if optimal yield can be achieved using only aphid-resistant soybeans. This would help farmers face the challenge of insecticide-resistant aphids in the future. An additional smaller-scale study was conducted in five states, that involved the same four options but in smaller plots to assess aphid-colonization in a fine-grained way. These replicated plots were also assessed once a week to determine if aphids colonized and established only on aphid-susceptible plants within the plots and if they spread from there. These data will inform modelling to determine the likely success of a Refuge-in-a-Bag resistance management plan for the soybean aphid.

4. Economic returns on resistant varieties: This is a three-summer study designed to assess the economic returns on herbicide tolerant and aphid resistant traits. We completed the second year of a field study replicated at two locations in Iowa to determine the optimal economic approach to pest management for soybean production. In 2016 and 2017, we compared four varieties that varied by aphid-resistance and herbicide-tolerance. In replicated plots, each variety was planted either early (May) or late (June) to determine if the yield potential varies. All varieties were treated with insecticide if aphid outbreaks occurred. Overall, aphid-resistant soybeans regardless of the background genetics prevented aphid outbreaks, and did not need an insecticide application. As observed in parts of Iowa and Minnesota, the insecticide applied to aphid-susceptible varieties did not provide expected control. Yield data are pending. So far, these data suggest that farmers can achieve the same yield by reducing inputs. For example, a conventional, non-herbicide tolerant variety with aphid-resistance produced the same yield as a herbicide tolerant variety without aphid-resistance. Going forward, the impact of aphid-resistance on the economics of soybean production will be explored in a collaboration with an economist to determine it’s potential return on investment.

IV. Biological Control

Regional survey of Aphelinus certus: Collaborators from 12 states in the NCSRP network provided information on soybean aphid pressure and the per-plant density of black (Aphelinus) parasitoid mummies in their respective states and sent samples of black mummies to the Heimpel laboratory at the University of Minnesota for identification. The highest soybean aphid pressure was reported in Minnesota and Iowa with soybean aphid presence reported in N. Dakota, S. Dakota, Nebraska, Wisconsin, Illinois, Indiana and Michigan as well. These trends compare very closely with the numbers of A. glycines captured by the Suction Trap Network, which confirmed that Kansas and Missouri had no reports of the aphid. The parasitoid A. certus was first reported in North Dakota on June 26th in the survey, and was found in Minnesota, Iowa, Illinois, Indiana and Michigan at densities between 0.6 and 2.0 parasitoids per plant by the end of summer. Aphelinus certus was the dominant parasitoid in the survey although the native parasitoid Lysiphlebus testaceipes was found in Iowa, Indiana, Michigan and Minnesota as well. The level of hyperparasitism was relatively high for Aphelinus at 21% and included species in the genera Alloxysta (Hymenoptera: Figitidae), Dendrocerus (Hymenoptera: Megaspilidae) and Syrphophagus (Hymenoptera: Encyrtidae). Overwintering and effectiveness of Aphelinus certus: In November 2016, wire-mesh cages containing mummies of three Aphelinus species (A. certus, A glycinis and A. rhamni) were placed in wooded areas near soybean fields, which mimic the habitats of the overwintering host of soybean aphids. Sites selected spanned from southern Iowa to central Minnesota. Mummies were recollected in April 2017 and allowed to emerge in laboratory growth chambers. These experiments revealed that all three species can survive winter conditions in Minnesota: of 1200 A. certus mummies placed in leaf-litter habitats, wasps emerged from 51.3% (616 wasps), compared with only 21.1% in foliar habitats, and 24.0% in the laboratory control. On the other hand, 64 emergence traps placed continuously in a soybean field from May through July 2017 captured only 1 Aphelinus certus wasp (in July), indicating that these wasps likely did not overwinter in the soybean fields. However, it is possible that the wasps emerged earlier in the spring than the sampling period, though doing so would require the wasps to immediately leave the soybean field to locate aphid hosts in alternative habitats.

View uploaded report PDF file

Final Project Results

Update:
This report covers Year 2 in a 3-year ongoing project on management and outreach of soybean insects in the North Central region. The report contains three sections. The first section is on the scientific and extension deliverables generated in Year 2 of this project. These deliverables all contain information generated in NCSRP-funded work. The second section is a narrative of current progress. The third section is a list of the project metrics written into our proposal for Year 2, and their status.

During the reporting period we published 33 scientific journal papers, gave 33 presentations at scientific meetings, and organized 2 scientific symposia on soybean pest management. Breeding efforts produced 4 varieties now under commercial production, and 8 experimental lines under field evaluation and experimentation. There were 18 students or postdocs graduated or in training on projects related to NCSRP research. We gave 75 extension presentations to farmers and other crop professionals containing NCSRP research. We wrote 18 extension articles and published 14 extension publications. A highlight of these publications is the field guide, Stink Bugs of the North Central Region, a field-friendly pocket-sized booklet on stink bug identification, biology and management. 6000 free hard copies of this field guide have been distributed through universities and state checkoff organizations, and made available as a free download on SRII and other websites. Other extension deliverables include hands-on scouting exercises designed to be used at winter meetings to teach soybean management techniques. During the reporting period we earned $588,000 in additional funding related to our NCSRP-generated research, showing the power of NCSRP funding to leverage resources for soybean research. Finally, members of our group received 6 awards for NCSRP-related work during the reporting period. In a noteworthy honor, we received the International IPM Award of Excellence for an IPM team. This award will be conferred at the 9th International IPM Symposium in March, 2018.

These deliverables are documented in detail in the attached version of this report.

View uploaded report PDF file

I. Extension and Outreach

We gave 75 extension presentations to farmers and other crop professionals containing NCSRP research. We wrote 18 extension articles and published 14 extension publications. A highlight of these publications is the field guide, Stink Bugs of the North Central Region, a field-friendly pocket-sized booklet on stink bug identification, biology and management. 6000 free hard copies of this field guide have been distributed through universities and state checkoff organizations, and made available as a free download on SRII and other websites. Other extension deliverables include hands-on scouting exercises designed to be used at winter meetings to teach soybean management techniques. These deliverables are documented in detail in the attached version of this report.

II. Insect Monitoring and Management

1. Stink bug monitoring and management: This is the second year of a 3-year study. The goal is to devise management thresholds for stink bugs that are specific to the North Central Region. In 2017, Michigan was added to the project, resulting in a total of 9 states. Work continues on identifying stink bugs from summer sampling and analyzing data. Some additional data collection will be conducted in Year 3 of the project, and final data analysis completed.

2. Pollinator diversity and soybean yield: The goal of this study is to document the diversity of pollinators present in soybean fields. Pollinators may enhance soybean yield, and soybean may serve as an important reservoir for pollinator biodiversity. Participants in ND, SD, IA, OH, MN, NE, IN, MO, WI collected pollinators in soybean fields. Bees identified from soybean to date include 5,513 individual bees representing 71 species in 17 genera and five families. This is an increase of 14 species compared to the 2014 survey. While only three states are done, the remaining six states (MO, IA, WI, MN, SD, ND) have two fields each and not as many individuals, so identification of bees is about 50% done. Syrphid flies (also important pollinators) will be identified after bees are finished. For the project to assess the diurnal activity of wild and managed bees in soybeans: Currently the EPA requires farmers to limit their application of insecticide to periods when bees are not on flowers to reduce exposure. Honey bees (and other bees) typically fly only during periods of daylight, which limits applications to dusk. Some commercial applicators have questioned whether honey bees are active throughout the entire day or if they limit their foraging to optimal periods of activity, when temperatures are not at their highest. In order to gain a better understanding of this topic we conducted a study to determine the diurnal activity of honey bees and other bees in soybean fields growing in a variety of environments along a nationwide transect, from Mississippi to South Dakota. Sampling took place once a week from R1 to R4. These data are still being processed. We are also planning how to approach this objective in Year 3 of the project, during the summer of 2018.

3. Soybean aphid insecticide resistance: The goals of this objective are to monitor for soybean aphid resistance to the insecticide thiamethoxam in the North Central Region, and to develop a DIY assay kit to test aphids for resistance to thiamethoxam insecticide. Our resistance monitoring has detected shifts in tolerance in certain soybean aphids, but the shifts are very low. We have also fine-tuned the bioassays used to monitor this resistance with various improvements. We have developed this technique to the point where it can be used as a research tool. However, we have concluded that it will not work to develop this as a “do-it-yourself” kit for ag professionals. We have tried many methods to make this user-friendly for crop consultants. However, the soybean aphid has proven too delicate for the DIY kit approach unless the end-user is trained to handle these types of insects. Too much soybean aphid injury and mortality occurs during aphid transfer. However, we have developed the methodology to the point where it is a useful research tool for trained researchers involved in resistance monitoring. Instead of further effort to develop a kit for widespread use, we are shifting our focus to aphid genetics as a component of resistance monitoring. Dr. Andrew Michel’s Lab (Ohio) has been assisting with genetic typing and development of clonal lineages. One hundred-sixty clonal populations were sent to Nebraska and each population is undergoing requisite population increase needed for bioassay.

4. Monitoring for aphids, thrips, and soybean vein necrosis: Soybean vein necrosis virus is transmitted by thrips. We sampled thrips from suction traps in 6 states. We have completed thrips survey for the 2016 growing season and begun processing the 2017 samples. There does not appear to be much thrips activity in May in most of the locations. Thrips populations start to increase in June which coincides with early vegetative stages of soybean in most Midwest states. The northern states don’t seem to have high thrips numbers even in June. Thrips activity peaked in July-August in most states and begins a decline in September. Populations of thrips vectors of SVNV are high during July-August in most locations. This coincided with appearance of the disease in IN but we did not receive any SVNV samples from other states. Regarding suction trap monitoring for soybean aphid population trends: The Midwest Suction Trap Network (MSTN) operates in 8 states with a total of 31 locations. A representative set of archival aphid slides from aphids collected in the MSTN have been made to be deposited in the INHS Insect Collection Museum. Online 3I Interactive Key for Aphis species in the Midwest USA has been updated to easy access http://dmitriev.speciesfile.org/key.asp?key=Aphis&lng=En&i=1&keyN=1). Suction trap samples collected in 2016 and 2017 have been shared with Punya Nachappa to monitor mainly soybean thrips. We have decided that the best home for the MSTN data is the Center for Invasive Species & Ecosystem Health at the University of Georgia (https://www.bugwood.org/). The suction trap data files are ready to be shared as soon as we communicate with the responsible of this database system. Moreover, emphasis on extension will be focus with the data collected from the MSTN.

5. Technology development: The goal is to develop an aphid-counting app. We are currently approximately 70% done with processing images collected over the past two summers (approx. 3000 total). Currently, mobile device cameras equipped with the android operating system are able to detect more aphids on infested soybean leaflets compared to iOS-based devices when using our aphid counting software. Work on this objective will continue in Year 3 of the project.


III. Resistant Varieties and Biotypes

1. Breeding for resistant varieties: The Diers program is developing and releasing soybean varieties with aphid resistance. The backcrossing of the aphid resistance genes Rag4 and Rag6 into cultivars that already have Rag1, Rag2, and Rag3 is continuing. During the summer of 2017, we produced BC3F1 seed for Rag6 in both the MG I Titan background and the MG II LD02-4485 background. The BC3F1 seed is being planted in the greenhouse so that the fourth and final backcross can be conducted early this winter. For Rag4, we completed the backcrossing of this gene in both backgrounds and now this gene is being combined with Rag1-3. In the LD02-4485 background, crosses were made this summer between plants with Rag4 backcrossed into them and Rag1-3 backcross plants. F1 seed from these crosses will be planted in the greenhouse to develop populations segregating for all four genes. In the Titan background, populations of F2 plants segregating for Rag1-4 were grown in the field this past summer. This winter we will grow plants in a greenhouse from these populations to identify those plants with the resistance allele for all four genes. These plants will then be crossed to backcross plants with Rag6 to complete the stacking of all five genes. Breeding to develop new cultivars with Rag1, Rag2 and stacks of Rag1 and Rag2 is continuing. Experimental lines with different combinations of these resistance genes were yield tested in 2017 and we are awaiting the completion of harvest so results from these tests can be summarized and selections made. In addition, commercial production or commercial scale seed increases are occurring for one variety with Rag1 only, four varieties with Rag2 only, and two varieties with Rag1 and Rag2 stacked together. These varieties are being sold under the Illini Brand name or are being licensed to other companies for their branding.

2. Aphid virulence genotyping and mapping: Our goal is to map aphid virulence. Genetic mapping of virulence has revealed segregation distortion among B1 and B2 reciprocal crossed. In other words, the ratio of genotypes in the F1 generation is not what was expected. Some offspring of this cross appear to be either sterile or inviable. Survivors in the F1 generation appear similar to the female genotype regardless of biotype (i.e. female drive). Reasons for this phenomena include disparate genetic divergence between biotypes 1 and 2 (which has also been observed), or drastically different bacterial symbionts (which is currently being studied). We observed high migration to buckthorn this past autumn and have made collections. These samples will be genotyped and compared to aphids already collected from 2017. Populations include Iowa, Minnesota and Ohio. Aphids from the above collections will also be screened for phenotyping on Rag varieties. Based on the segregation distortion and female drive, we are comparing and genotyping Wolbachia from the soybean aphid. Wolbachia is a bacteria that can be found within insects that often induces mating incompatibilities. If indeed crosses of B1 and B2 are infertile, then the spread of virulence may be more rapid and place more emphasis on a refuge.

3. Aphid virulence management for resistant varieties: During the 2017 growing season we completed a field study in three states (Iowa, South Dakota, and Ohio) in quarter-acre, replicated plots to measure the impact of a Refuge-in-a-Bag approach to using aphid-resistant soybeans. The purpose of this study is to find ways to maximize the longevity of aphid resistant varieties while minimizing yield loss in refuges. Data from 2017 are being analyzed. Another field season of data will be collected in Year 3 of this study. Preliminary data assessments from Iowa show that all options using the aphid resistant line, regardless of how much susceptible soybean was mixed in, had lower aphid populations than the plots with only aphid-susceptible soybeans. These data will inform modelling to determine the likely success of a Refuge-in-a-Bag resistance management plan for the soybean aphid.

4. Economic returns on resistant varieties: This is a three-summer study designed to assess the economic returns on herbicide tolerant and aphid resistant traits. We completed the second year of a field study replicated at two locations in Iowa to determine the optimal economic approach to pest management for soybean production. In 2016 and 2017, we compared four varieties that varied by aphid-resistance and herbicide-tolerance. In replicated plots, each variety was planted either early (May) or late (June) to determine if the yield potential varies. All varieties were treated with insecticide if aphid outbreaks occurred. Overall, aphid-resistant soybeans regardless of the background genetics prevented aphid outbreaks, and did not need an insecticide application. As observed in parts of Iowa and Minnesota, the insecticide applied to aphid-susceptible varieties did not provide expected control. Yield data are pending. So far, these data suggest that farmers can achieve the same yield by reducing inputs. A third field season of experiments will be conducted in Year 3 of this study.

IV. Biological Control

We worked with researchers from 12 states in the NCSRP network, and each scouted three times over the summer of 2017. They provided information on soybean aphid pressure and the per-plant density of black (Aphelinus) parasitoid mummies in each state, and sent samples of black mummies to the Heimpel laboratory at the University of Minnesota for identification. Soybean aphid was first detected in June across the northern tier of states - North Dakota, Minnesota, Iowa, Wisconsin, and Michigan (see maps, below). By mid July there were high densities of aphids in North Dakota, Minnesota, Iowa, and Illinois, and aphids reported in South Dakota and Nebraska; Minnesota had aphid densities above the economic threshold of 250 aphids per plant. In August soybean aphid pressure above the action threshold was reported in Minnesota and Iowa, substantial aphid numbers were found throughout the region, but no aphids were reported for the entire summer in Kansas, Missouri, and Ohio. These trends compare very closely with the numbers of A. glycines captured by the Suction Trap Network, which confirmed that Kansas and Missouri had no reports of the aphid.

The parasitoid A. certus was first reported in North Dakota on June 26th, and was found in Michigan in June as well. The parasitoid was also found in Minnesota, Iowa, Illinois, and Indiana at densities between 0.6 and 2.0 parasitoids per plant by the end of summer. A pattern of the aphid and its parasitoids seems to be centered in the north and west, spreading south and east during the summer but remaining most prevalent in Minnesota and Iowa. The parasitoid, and to some extent the aphid as well, was first detected in the northwest, in the relatively small soybean acreage of North Dakota, and despite movement southward, neither the parasitoid nor the aphid were detected in the southernmost nor easternmost states.
Aphelinus certus was the dominant parasitoid in the survey although the native parasitoid Lysiphlebus testaceipes was found in Iowa, Indiana, Michigan, and Minnesota as well. The level of hyperparasitism was relatively high for Aphelinus at 21% and included species in the genera Alloxysta (Hymenoptera: Figitidae), Dendrocerus (Hymenoptera: Megaspilidae), Asaphes (Hymenoptera: Pteromalidae), and Syrphophagus (Hymenoptera: Encyrtidae).

Benefit to Soybean Farmers

Projects within these program areas include the creation and distribution of extension deliverables, stink bug monitoring and management, studies on the ability of pollinators to increase yield potential, monitoring for soybean aphid insecticide resistance, breeding for aphid-resistant varieties, genotyping and mapping virulent aphid biotypes that overcome resistant varieties, developing virulence management strategies, and the determining economic return on resistant varieties. All of these objectives are designed to make soybean production more profitable and sustainable, and they were designed with feedback from soybean farmers. These priorities for soybean entomology were determined through a needs-assessment process in 2014 and early 2015. We obtained and compiled feedback from a focus group and survey of producers, industry personnel, and other stakeholders, focus groups with soybean entomology research and extension faculty, and discussions with soybean checkoff boards, in order to identify and address the top entomological needs in the region.

Performance Metrics

I. Extension and Outreach.

Goal: Produce at least three extension deliverables.

Outcome: Goal met, with 14 extension publications stemming from NCSRP research.


II. Insect Monitoring and Management

1. Stink bug monitoring and management

Goals: Continued sample processing; Data analysis; Revise protocols; Identify study fields and staff

Outcomes: all goals met

2. Pollinator diversity and soybean yield

Goals: Species identification for sampling continues; Data analysis for sampling; Present sampling results; Contribute to extension deliverables; Hire graduate student for yield study

Outcomes: all the goals were met except the final one, to purse a pollinator/yield study. As described in previous progress reports, we have changed this objective to focus instead on the times of day when pollinators are present in soybean.


3. Soybean aphid insecticide resistance

Goals: Communicate results of DIY monitoring; Begin constructing protocol for chlorpyrifos and L-cyalothrin bioassay

Outcomes: DIY monitoring has been deemed not feasible due to the fragility of the insect, and instead the technique is being adapted as a research tool for trained researchers.

4. Monitoring for aphids, thrips, and soybean vein necrosis

Goals: Weekly trap monitoring in summer; Communicate trap data to collaborators for extension and research; Thrips sampling; Thrips sample processing begins

Outcomes: all goals met

5. Technology development

Goals: Refine sampling algorithm; Collect additional images from different device types; Develop node-based sampling integrated with counting algorithm

Outcomes: The first two goals have been met. Work continues on the third goal.

III. Resistant Varieties and Biotypes

1. Breeding for resistant varieties
Goals: Analyze data from year 1; Grow backcross plants and make crosses; Test segregating populations; Yield tests

Outcomes: all goals met
2. Aphid virulence genotyping and mapping
Goals: Determine inheritance of virulence; Genotype F1 and F2 populations; Chromosome linkage map

Outcomes: goals have not been fully met but work on them continues

3. Aphid virulence management for resistant varieties
Goals: Increase cultivars; Determine experimental protocol; Field experiment, year 2; Data analysis

Outcomes: all goals have been met except data analysis of year 2 data, which is still underway

4. Economic returns on resistant varieties

Goals: Field experiment, year 2; Data analysis

Outcomes: the field experiment was performed in year 2; data analysis is still underway


IV. Biological Control

Goals: Coordinate parasitoid collection with collaborating states; Conduct releases of A. glycinis and A. rhamni

Outcomes: all goals met

Project Years