Project Details:

Title:
Improving soybean IPM tactics in Iowa

Parent Project: Improving soybean IPM tactics in Iowa
Checkoff Organization:Iowa Soybean Association
Categories:Insects and pests
Organization Project Code:021677
Project Year:2020
Lead Principal Investigator:Erin Hodgson (Iowa State University)
Co-Principal Investigators:
Keywords: aphis glycines Matsumura, Foliar, gall midge, host plant resistence, Insect, insecticide, Integrated Pest Management, Seed Treatments, Soybean Aphid

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

My research lab has the nation’s largest soybean aphid efficacy evaluation program, and has mainly focused on foliar insecticide performance. I have access to new products or improved formulations before they are commercially available, and farmers can see performance data of new products compared to traditional insecticides. I want to grow my program beyond foliar insecticides with additional management tools like host plant resistance. My research is novel in that I 1) use replicated plots to compare seed- and foliar-applied insecticides, 2) collect intense data on soybean aphid seasonal exposure, 3) compare insecticide performance to host plant resistance, and 4) present unbiased data from multiple industry companies.

Project Objectives

Proposed Work:
During the summers of 2019-2020, experimental plots will be used to evaluate insect management tactics, like seed treatments, foliar insecticides, and host plant resistance (see previous reports here: www.ent.iastate.edu/soybeanresearch/content/extension). These tactics will be evaluated alone and in combination to determine optimum yield protection. Plots will be established at Iowa State University Research Farms each summer. At each location, 20-35 treatments will be replicated four times in a randomized complete block design using a 30" row spacing. Insect activity will be monitored weekly (e.g., soybean aphid, soybean gall midge, Japanese beetle, stink bugs, caterpillars, etc.), and foliar applications will be based on treatment thresholds. At the end of each season, yield will be collected and cumulative aphid days will be generated for each treatment.

Communications and outreach strategies:
I have a 70% field crops extension appointment at Iowa State University (ISU). Throughout the project, I will actively participate in extension programs that summarize efficacy data and promote sustainable soybean pest management. Field day demonstrations and winter programs will be coordinated with ISU Extension and Outreach, Iowa Soybean Association, industry partners, and other organizations. Potential ISU Extension and Outreach programs include: Integrated Crop Management Conference, Crop Advantage Series, and the numerous field day demonstrations with ISU. Participants will largely be farmers, but will also include crop consultants, agricultural professionals and other ISU personnel. In addition, I will publish annual research findings in a Yellow Book (www.ent.iastate.edu/soybeanresearch/content/extension). As a way to deliver real-time updates on soybean pests in the summer, I will continue publishing podcasts with Matt O’Neal, posting informal articles to ICM Blog, and contributing articles to ICM News.

Project Deliverables

Data collected every summer will become publically available:
• Yellow Book for Soybean Insects is free and available electronically at my lab website.
• Arthropod Management Tests publication will be generated annually. These publications are nationally recognized for insecticide efficacy evaluations and available to Entomological Society of America members.
• Regular updates about soybean aphid and other pests are available throughout the year through ICM News, ICM Blog, and podcasts.

As an example of my extension activity related to soybean pest management in 2017, I created the following products and activities:
• 3 refereed journal articles
o The biology and economics behind soybean aphid insecticide recommendations [Plant Health Progress]
o Arthropod Management Tests [ESA publication]
o Getting to Know the Insects [ISUEO publication]
• 1 proceeding article for non-scientific audience
• Yellow Book for soybean aphid efficacy evaluations (Hodgson and VanNostrand 2016)
• 3 articles in ICM News [5,500 subscribers]
• 13 presentations [~1,200 people]
• 1 video for Private Applicator Training

Progress of Work

Updated April 30, 2020:
Spring planting conditions throughout Iowa were first cold and wet in 2019, and most soybean fields were planted later to accommodate corn planting. Then May was normal and June was wetter than normal in many locations throughout Iowa. Population fluctuations between locations and years is typical soybean aphid dynamics for Iowa. Soybean aphids arrived on soybean in July, slightly behind average infestation dates. Soybean aphid colonization was initially patchy and continued to grow at a slow pace, likely due to hot evenings providing little relief to adults. Some commercial fields experienced exponential growth of soybean aphid after bloom, especially in northern Iowa. However, few fields in northwestern and northcentral counties had soybean aphid exceed the economic threshold. Some populations did persist until after seed set (R5–R6), but very quickly crashed at most locations by mid-September. When applications had sufficient coverage and applied at the labeled rate, efficacy for soybean was good (i.e., >95% knockdown within three days after application) throughout most of Iowa. I was able to complete proposed work, including research and extension related to soybean aphid management. I established a foliar insecticide efficacy evaluation at one location in 2019 (northwest Iowa). I had 25+ treatments including soil-applied and foliar insecticide applications.
In addition to soybean aphid, Japanese beetle, bean leaf beetle, and soybean gall midge were prevalent in some Iowa soybean fields. I ended up spending a lot of time responding to questions and concerns about soybean gall midge. By the end of 2019, this new pest was confirmed along western Iowa in 26 counties (up from 18 in 2018):
I did not conduct any research on this pest, but did work with ISU Research Farm Managers, Iowa Soybean Association staff and farmers. This soybean pest is particularly devastating and can cause plant death. Affected plants were restricted to field edges and economic loss could be 100%. I dedicated many extension programs to soybean gall midge and spoke about the limited information on biology, life cycle and management. My program raised awareness of this new soybean pest and am arranging efficacy evaluations and a germplasm screening for 2019 at several locations.

My extension efforts for soybean IPM in 2019-2020 are summarized here:

Peer-Reviewed Extension Publications and Proceedings: 4
Hodgson, E. W., A. N. Dean, and Z. Wang. 2019. Using immediate feedback cards in extension.
Journal of Extension, in press April 2020.

Hodgson, E. W., and G. VanNostrand. 2020. Soybean aphid efficacy screening program, 2019.
Entomological Society of America Arthropod Management Tests. DOI: 10.1093/amt/tsaa053.

Lagos-Kutz, D., D. J. Voegtlin, D. Onstand, D. Hogg, D. Ragsdale, K. Tilmon, E. Hodgson, C. DiFonzo,
R. Groves, C. Krupke, J. LaForest, N. J. Seiter, E. Duerr, B. Bradford, and G. L. Hartman. 2020. The
soybean aphid suction trap network: sampling the aerobiologcal “soup.” American Entomologist.
DOI: 10.1093/ae/tmaa009.

Other Extension Publications:
3 proceedings
32 ICM News, Blog and Encyclopedia articles

Extension presentations:
Invited talks: 3
Other talks: 36
Field days: 12

Extension Videos: 4

Updated October 30, 2020:

Final Project Results

Updated October 30, 2020:
Spring planting conditions throughout Iowa were excellent and ahead of historical planting records. In general, drought conditions were evident and field in western Iowa, in particular, were stressed. Abnormally dry or moderate drought conditions persisted throughout the entire growing season. On August 10, a derecho moved through central Iowa and caused plant damage to commercial soybean.
Population fluctuations between locations and years is typical soybean aphid dynamics for Iowa. Soybean aphids arrived on soybean in July, which is average for Iowa. Soybean aphid colonization was initially patchy and continued to grow at a slow pace. Some commercial fields experienced exponential growth of soybean aphid after bloom, especially in northern Iowa. Several fields in northwestern and northcentral counties had soybean aphid exceed the economic threshold. Some populations did persist until after seed set (R5–R6), but very quickly crashed at most locations by mid-September. When applications had sufficient coverage and applied at the labeled rate, efficacy for soybean was good (i.e., >95% knockdown within three days after application) throughout most of Iowa. I was able to complete proposed work, including research and extension related to soybean aphid management. I established a foliar insecticide efficacy evaluation at one location in 2019 (ISU Northwest Research Farm). I had 25+ treatments at this location where aphids exceeded the economic threshold. The complete 2020 summary will be available in December.
Soybean gall midge continues to emerge as an economic pest in Iowa. Five new counties were confirmed with infestations (total of 31 counties), and expanded to 114 total counties in five states (IA, MN, MO, NE, SD). I dedicated many extension programs to soybean gall midge and spoke about the limited information on biology, life cycle and management. Overall, severity of commercial fields was less than in 2019 and infestations tended to be more scattered within fields. I established efficacy evaluations at two locations in 2020. Multiple chemistries and sites of application were used, but emphasis was placed on suppressing overwintering adult establishment. Our 25+ treatments did not appear to delay or effectively suppress larval feeding.
In addition, there were a variety of caterpillar species present in soybean in 2020. Thistle caterpillar was not as abundant as in 2020 but the first generation in Iowa was higher than normal. Japanese beetle and bean leaf beetle populations were typical and spotty in commercial fields. Twospotted spider mites were obvious and sometimes an economic issue later in the season and is attributed to drought-stressed crops.

View uploaded report Word file

What does it mean for farmers: Effective management tactics are still limited for soybean gall midge, but our recommendations for best efforts to reduce the severity of plant injury are to:
• Plant soybeans last in areas (e.g., late May or early June) where heavy soybean gall midge pressure has been observed in previous years.
• Scout field edges first for initial detection of infested plants.
• Apply foliar insecticides at the time of adult emergence, typically around V3-V5 growth stages. Perimeter treatments may be a more cost-effective strategy at early vegetative growth.
• Additional insecticides may be required to suppress additional emergence.

What does it mean for farmers: Population fluctuations between locations and years is typical soybean aphid dynamics for Iowa. Our recommendation for soybean aphid management in Iowa is to:
• Strongly consider using host plant resistance if soybean aphid populations are persistent and the seed agronomic traits are appropriate for the area. The use of a pyramided gene will result in lower seasonal accumulation and reduce the need for foliar insecticides.
• Plant early if the field is in an area with persistent soybean aphid populations.
• Scout for soybean aphid, especially during R1–R5, and use a foliar insecticide if aphids exceed the economic threshold of 250 per plant.
• Use a product labeled for soybean aphid; most well-timed applications of foliar insecticides will provide yield protection if applied at the economic threshold and coverage is sufficient.
• Evaluate foliar insecticide efficacy three days after application to ensure soybean aphid populations were sufficiently reduced.
• Understand that late-season accumulation of aphids (i.e., after R5) may not impact yield like it does in early reproductive growth; a foliar insecticide applied after seed set may not be an economically profitable choice.

Benefit to Soybean Farmers

• recognize soybean aphid and other soybean pests [short term skill];
• improve general pest management approaches, including the effect of multiple pests and the potential for cumulative injury [short term skill];
• implement scouting and adopt economic thresholds for soybean pests [long term skill];
• become aware and understand the benefits of host plant resistance for soybean aphid [short term knowledge];
• reduce insecticide use, including seed and foliar treatments [long term skill];
• increase adoption of host plant resistance on commercial farms [long term skill];
• understand the implications for soybean aphid genetic resistance to insecticides [long term knowledge]; and
• improve profit margins by reducing input costs [long term knowledge].

Performance Metrics

Project Years