Update:
Initially, the 2018-2019 winter temperatures were relatively warm compared to previous years in Iowa (mean temperature of 28 degrees in December). However, February 2019 was exceptionally cold statewide (mean temperature of 15 degrees). April planting conditions throughout Iowa were cold and wet, and most soybean fields were planted later to accommodate corn.
The most abundant insect statewide was thistle caterpillar. Although noted every year, populations were high and sometimes economic. Other caterpillars were also observed (e.g., green cloverworm, alfalfa caterpillar, and soybean looper). Soybean gall midge was prevalent throughout the western counties. This new soybean pest was devastating to plants, especially near the field edge, with yield losses ranging from 20-100%. Soybean aphids arrived to Iowa soybean in July, after full bloom. Aphid populations were initially patchy and slowly spread within and between fields. In August, some populations grew quickly and exceeded the economic threshold. When foliar applications had sufficient coverage and were applied at the labeled rate, efficacy for soybean aphid was good (i.e., >95% knockdown) throughout Iowa. Other notable soybean insect pests included Japanese beetle and bean leaf beetle.
I was able to complete proposed work, including research and extension related to soybean aphid management. We established plots at one ISU Research Farm in northwestern Iowa in 2019. In total, we evaluated 27 treatments with six insecticidal group/subgroups. The plots were initially colonized by soybean aphid in July, with exponential growth in August. There were a few other soybean insect pests present (e.g., Japanese beetle, colaspis beetles, thistle caterpillar, and stink bugs), but economic populations were not evident. Natural enemies, such as beetles, flies, lacewings and wasps, were present throughout the reproductive stages, but did not significantly affect aphid populations. The threshold was reached on 15 August and plots were sprayed on 16 August. Plants were at R5 (beginning seed set) at the time of the foliar application. Soybean aphid populations peaked on 5 September after full seed set with 1,783.33 per plant. As demonstrated in previous efficacy evaluations, yield losses are not as dramatic when aphids peak after full seed set. Although the untreated control had numerically less yield than all other treatments, there was much overlap between treatments.
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 CAD 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 CAD (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.
Extension publications:
McMechan, J. and E. Hodgson. Soybean gall midge: ecology and potential management strategies, pp. 89-93. In Proceedings: 31st Annual Iowa State University Integrated Crop Management Conference, Ames, IA, 4-5 December 2019.
Dean, A., M. O’Neal, E. Hodgson, I. Valmorbida, J. Hohenstein, and B. Coates. Building a budget for pest resistance, pp. 69-73. In Proceedings: 31st Annual Iowa State University Integrated Crop Management Conference, Ames, IA, 4-5 December 2019.
Hodgson, E. W., and G. VanNostrand. 2019. Soybean aphid efficacy screening program, 2018. Entomological Society of America Arthropod Management Tests. DOI: 10.1093/amt/tsz013.
Shanovich, H. N., A. D. Dean, R. L. Koch, and E. W. Hodgson. 2019. Biology and management of Japanese beetle (Coleoptera: Scarabaeidae) in corn and soybean. Journal of Integrated Pest Management. DOI: 10.1093/jipm/pmz009.
Hodgson, E. W. On the lookout for a new soybean pest, p. 14. In Proceedings: Iowa State University Crop Advantage Series, Ames, IA, January 2019.
Hodgson, E. W., G. VanNostrand, A. Dean, and M. Helton. 2019. 2019 Yellow Book Report of insecticide evaluation for soybean pests, 36 pp. Department of Entomology, Iowa State University, Publication CROP 3197.
Hodgson, E. “Japanese beetles get a slow start to 2019.” In ICM News. 16 June 2019.
Hodgson, E. “Soybean gall midge confirmed in Iowa and Nebraska.” In ICM News. 15 June 2019.
Hodgson, E. “Seedcorn maggots flying in Iowa.” In ICM News. 13 May 2019. 225. Hodgson, E. “Soybean aphid egg hatch starting in northern Iowa.” In ICM News. 2 May 2019.
Hodgson, E. “Will the insects survive this winter?” In ICM News. 20 February 2019.
Hodgson, E. “2018 Insecticide evaluation for soybean aphid.” In ICM News. 28 January 2019.
Hodgson, E. “When is it too late to spray for soybean aphid?” In ICM News. 8 August 2018.
Extension presentations:
Hodgson, E. W. #IPM: how do we build resilient, sustainable pest management crop systems? University of Minnesota Extension Crop Pest Management Short Course, Minneapolis, MN [325 people] 12 December 2018
McMechan, J., E. Hodgson, T. Hunt, B. Potter, B. Wright, and A. Varenhorst. 2019. Soybean gall midge: an emerging soybean pest. S1080 Annual Working Group Meeting, Cleveland, OH. [25 people] 25 January 2019
Hodgson, E. W. Field crop pest management update for 2019. Iowa State University Extension and Outreach Ag Chem Dealer Update.
- Iowa City, IA. [90 people] 17 December 2019
- Ames, IA. [75 people] 18 December 2019
Dean, A., M. O’Neal, E. W. Hodgson, J. Hohenstein,and B. Coates. Building a budget for pest resistance. Iowa State University Extension and Outreach Integrated Crop Management Annual Conference, Ames, IA. [2 sessions; 125 people] 4 December 2019
Hodgson, E. W., and A. Dean. Insect identification, sampling and management. Iowa State University Extension and Outreach Crop Scout School, Ames, IA. [75 people] 30 March 2019
Hodgson, E. W. Field crop insect mashup. Iowa State University Northcentral Research Farm Annual Meeting, Wesley, IA. [50 people] 6 March 2019
Hodgson, E. W. Soybean gall midge is a new soybean pest. Pioneer Sales Team Winter Meeting, Ames, IA. [75 people] 1 March 2019
Hodgson, E. W. Field crop insect mashup. WinField United Iowa Regional Conference, Ames, IA. [225 people] 21 February 2019
Hodgson, E. W. Soybean gall midge in Iowa. Iowa Soybean Association Farmer Research Tour, Storm Lake, IA. [85 people] 5 February 2019
Hodgson, E. W. Soybean gall midge is a new soybean pest. 2019 Iowa State University Extension and Outreach Crop Advantage Series Workshops.
- Sheldon, IA. [18 people] 3 January 2019
- Burlington, IA. [16 people] 4 January 2019
- Storm Lake, IA. [12 people] 8 January 2019
- Ames, IA. [125 people] 9 January 2019
- Honey Creek, IA. [2 sessions; 10 people] 10 January 2019
- Fort Dodge, IA. [2 sessions; 100 people] 16 January 2019
- Davenport, IA. [2 sessions; 120 people] 18 January 2019
- Le Mars, IA. [50 people] 22 January 2019
- Atlantic, IA. [100 people] 24 January 2019
- Iowa City, IA. [2 sessions; 58 people] 29 January 2019
- Denison, IA. [80 people] 30 January 2019
Hodgson, E. W. Field crop mashup for 2018. Iowa State University Extension and Outreach Crop Clinic for Worth and Cerro Gordo Counties, Manly, IA. [60 people] 14 December 2018
Hodgson, E. W. Soybean gall midge is a new soybean pest. Iowa State University Extension and Outreach Ag Chem Dealer Update.
- Iowa City, IA. [85 people] 11 December 2018
- Ames, IA. [63 people] 12 December 2018
Hodgson, E. W. and. J. McMechan. A fly in the ointment: soybean gall midge is a new pest. Iowa State University Extension and Outreach Integrated Crop Management Annual Conference, Ames, IA. [2 sessions; 230 people] 28 November 2018
Hodgson, E. Field crop pest updates. Northern Research Farm, Iowa State University, Kanawha, IA. [45 people] 5 September 2019
Hodgson, E. Field crop pest updates. Northeast Research Farm, Iowa State University, Nashua, IA. [2 sessions; 75 people] 28 August 2019
Hodgson, E. Insect updates. Dekalb Field Day, Field Extension Education Laboratory, Iowa State University, Ames, IA. [2 sessions; 25 people] 8 August 2019
Richardson, J.,and E. Hodgson. Insect identification and scouting in field crops. Corteva Field Day, Field Extension Education Laboratory, ISU, Ames, IA. [6 sessions; 60 people] 23 July 2019
Hodgson, E. Soybean gall midge update. Armstrong Research Farm, Iowa State University, Lewis, IA. [75 people] 18 July 2019
Hodgson, E. Soybean defoliation and pest management. Management Clinic, Field Extension Education Laboratory, Iowa State University, Ames, IA. [22 people] 11 July 2019
Hodgson, E. Soybean gall midge update. Northwest Research Farm, Iowa State University, Sutherland, IA. [3 sessions; 135 people] 10 July 2019
Hodgson, E. Insect ID and scouting in field crops. Corteva New Agronomists Field Day, Field Extension Education Laboratory, ISU, Ames, IA. [3 sessions; 75 people] 9 July 2019
Hodgson, E. Soybean aphid management update. Northcentral Research Farm, Iowa State University, Kanawha, IA. [3 sessions; 85 people] 20 June 2019
Hodgson, E., and A. Dean. Seed and seedling pest management in field crops. Early-Season Clinic, Field Extension Education Laboratory, Iowa State University, Ames, IA. [2 sessions; 40 people] 16 May 2019
View uploaded report 
This project was able to successfully evaluate three pests in 2019: soybean aphid, Japanese beetle and soybean gall midge. From these evaluations, farmers will have a better understanding of effective insectide options for managing common soybean insect pests.
In particular, for soybean aphid, which has been evaluated for more than 10 years, these data become a historical database for comparison of traditional and new chemistries. In 2019, we were able to demonstrate a late-season application did not produce a typical yield response. My recommendation is to not spray if aphids exceed the economic threshold at or after full seed set.
For Japanese beetle, we evaluated a few products. Our data suggests insecticides do not have the residual to keep these mobile pests away from sprayed fields.
Soybean gall midge was first evaluated in 2019, and it was a difficult pest to manage. Treatments did not successfully protect yield; however, the later-planted location did seem to avoid more severe plant injury.