Purpose: 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 standard 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, and 3) present unbiased data from multiple industry companies.

Proposed work: During the summers of 2021-2023, experimental plots will be used to evaluate insect management tactics, like seed treatments and foliar insecticides (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 high-risk locations in Iowa each summer.

1) Soybean aphid. At one location, 20-30 treatments will be replicated four times in a randomized complete block design using a 30" row spacing. Treatments will include a range of insecticidal groups and application sites. Aphid population dynamics will be monitored weekly in addition to secondary pest activity (e.g., beetles, mites, stink bugs, caterpillars, etc.). Foliar applications will be based on our established treatment threshold for soybean aphid. At the end of each season, yield will be collected and compared to cumulative aphid days for each treatment.
2) Soybean gall midge. At two locations, 20-30 treatments will be replicated four times in a randomized complete block design using a 30" row spacing. Midge larval will be monitored weekly in addition to secondary pest activity (e.g., soybean aphid, beetles, mites, stink bugs, etc.). A combination of seed-applied and foliar treatments will be evaluated. Foliar applications will be based on our observation of overwintering adult emergence (See 2a). At this point, that is our “best guess” for targeting adult movement into soybean. At the end of each season, yield will be collected and compared to insect activity for each treatment.
a. Adult emergence cages. To help determine spray recommendations, we will use “Illinois style” soil emergence cages in currently planted cornfields to collect adult soybean gall midges. During the summer, cages will be moved to currently growing soybean to help refine life table characteristics (life cycle duration, emergence duration, etc.).
b. Injury-severity model. As with corn rootworm, we plan to create a 0-3 plant injury scale for soybean gall midge and develop a model for yield loss prediction (Tinsley et al. 2012). The injury scale and model will help farmers and crop consultants better estimate larval infestations and expected yield loss in future growing seasons. The data collected from this proposed project will directly feed into validating the scale with the model. Preliminary data from 2019 is shown in Figure 1.
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 posting informal articles to ICM Blog and contributing articles to ICM News.

Update:
General project summary:
The 2020-2021 winter was relatively warm compared to previous years in Iowa (mean temperature of 27.85 degrees in December). April had cooler than average temperatures but planting conditions were favorable throughout much of the state. Planting progress was about two weeks ahead of the average. Soybean acres were up 500,000 compared to 2019 (9.9 million acres planted). Drought was prevalent in western Iowa and reached “Extreme Drought” or D3-4 status in some Iowa counties in August.

Soybean pests continue to be highly variable throughout Iowa. Several caterpillar and beetle species were present, but generally at non-economic levels. Soybean aphids arrived to Iowa soybean in July. Aphid populations were initially patchy and slowly spread within and between fields. In August, some populations grew quickly and exceeded the economic threshold. Sometimes, populations peaked in late August or early September. Although soybean aphids did not reach the economic threshold in our research plots, we noted plots sprayed with pyrethroids did not yield as well as other treatments. With the help of ISU graduate student, Ivair Valmorbida, we were able to confirm this aphid population to be pyrethroid-resistant.
In addition to soybean aphid, soybean gall midge was prevalent in some Iowa soybean fields. 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 continue to address questions and concerns about soybean gall midge. This new pest was confirmed along western Iowa in 35 counties (4 new county detections in 2021). I had several field experiments in western Iowa in 2021. I dedicated many extension programs to soybean gall midge and spoke about the limited information on biology, life cycle and management. Adult soybean gall midge emergence began mid-June and midge-infested plants were found shortly after. Adult emergence was almost completely continuous throughout the summer, with three generations of adults being observed.

My extension efforts are summarized here:
Extension publications:
Sisson, A. J., D. S. Mueller, S. P. Conley, C. K. Gerber, S. H. Graham, E. W. Hodgson, T. R. Leglieter, P. P. Price, K. J. Schaefer, E. J. Sikora, T. H. Wilkerson, and K. L. Wise. 2021. Crop scouting basics for corn and soybean. Crop Protection Network CPN 4007. DOI: 10.31274/cpn-20201214-0.

Extension presentations:
Hodgson, E. W. Let’s get real about soybean insecticides: what’s in and works. Crop Pest Management Short Course, Minneapolis, MN [2 sessions; 225 people] 8 December 2021
Dean, A., E. Hodgson, and C. Pilcher. “Updates on chlorpyrifos uses in 2022. In ICM News. 10 March 2022.
Dean, A., and E. Hodgson. “2021 regional corn rootworm monitoring network summary available.” In ICM News. 27 January 2022.
Hodgson, E., and A. Dean. “Fall armyworm is a 2021 late-season pest.” In ICM News. 2 September 2021.
Hodgson, E. “Soybean gall midge emergence beginning in Iowa.” In ICM News. 17 June 2021.
Hodgson, E. “Twospotted spider mite scouting reminders.” In ICM News. 28 July 2021.
Hodgson, E. W., and A. Dean. Soybean gall midge and fall armyworm management. 2022 Iowa State University Extension and Outreach Crop Advantage Series Workshops.
- Sheldon, IA. [8 people] 6 January 2022
- Storm Lake. IA. [10 people] 7 January 2022
- Le Mars, IA. [13 people] 26 January 2022
Hodgson, E. W. Soybean gall midge and soybean aphid management update. Stine Annual Summer Meeting, Adele, IA. [75 people] 21 July 2021
Hodgson, E. Management updates for corn and soybean pests. Stine Field Day, Field Extension Education Laboratory, Iowa State University, Ames, IA. [3 sessions; 55 people] 30 July 2021
Hodgson, E. Corn rootworm and soybean gall midge updates. Northwest Research Farm, Iowa State University, Sutherland, IA. [125 people] 7 July 2021

Extension Webinars:
Dean, A., and E. W. Hodgson. Tolerances revoked for chlorpyrifos: what are some other options? Loveland/Nutrien Regional Meeting Virtual Delivery [25 March 2022]
Hodgson, E. W., B. Kolbe, and J. McMechan. Using tillage to reduce overwintering soybean gall midge. Soybean gall midge discussion series, Virtual Delivery. 22 February 2022
Hodgson, E. W., and J. McMechan. Soybean gall midge ID, distribution, scouting tips, and injury score. Soybean gall midge discussion series, Virtual Delivery. February 2022

Extension Videos:
Dean, A., M. O’Neal, and E. W. Hodgson. Developing a decision-making framework for pest management. Soybean Breeders’ Workshop, Virtual Delivery [23 February 2021]

View uploaded report

Update:
The 2020-2021 winter was relatively warm compared to previous years in Iowa (mean temperature of 27.85 degrees in December). April had cooler than average temperatures but planting conditions were favorable throughout much of the state. Planting progress was about two weeks ahead of the average. Soybean acres were up 500,000 compared to 2019 (9.9 million acres planted). Drought was prevalent in western Iowa and reached “Extreme Drought” or D3-4 status in some Iowa counties in August.

Soybean pests continue to be highly variable throughout Iowa. Several caterpillar and beetle species were present, but generally at non-economic levels. Soybean aphids arrived to Iowa soybean in July. Aphid populations were initially patchy and slowly spread within and between fields. In August, some populations grew quickly and exceeded the economic threshold. Sometimes, populations peaked in late August or early September. Although soybean aphids did not reach the economic threshold in our research plots, we noted plots sprayed with pyrethroids did not yield as well as other treatments. With the help of ISU graduate student, Ivair Valmorbida, we were able to confirm this aphid population to be pyrethroid-resistant.

In addition to soybean aphid, soybean gall midge was prevalent in some Iowa soybean fields. 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 continue to address questions and concerns about soybean gall midge. This new pest was confirmed along western Iowa in 35 counties (4 new county detections in 2021). I had several field experiments in western Iowa in 2021. I dedicated many extension programs to soybean gall midge and spoke about the limited information on biology, life cycle and management. Adult soybean gall midge emergence began mid-June and midge-infested plants were found shortly after. Adult emergence was almost completely continuous throughout the summer, with three generations of adults being observed.

What does it mean for farmers: Effective management tactics for soybean gall midge are still limited for this pest, 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.

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.