Project Details:

Title:
Evaluating soybean aphid management with an expanded toolbox

Parent Project: Evaluating soybean aphid management with an expanded toolbox
Checkoff Organization:Iowa Soybean Association
Categories:Insects and pests, Education, Sustainability
Organization Project Code:
Project Year:2018
Lead Principal Investigator:Erin Hodgson (Iowa State University)
Co-Principal Investigators:
Keywords: Insecticide Resistance, Insecticides, Soybean Aphid (SA), Soybean Aphid - Monitoring

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

Project Deliverables

Timeline: projected research and extension activities will be the same:
• Winter: present lectures at meetings.
• Spring: hire undergraduate student; treat seeds; purchase field and spray equipment; establish plots; plant seed; and present at summer meetings.
• Summer: collect agronomic and pest-related data; and apply foliar treatments.
• Fall: harvest plots; and write summary reports (e.g., Yellow Book and AMT).

Expected Outputs: 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.

Progress of Work

Updated April 11, 2018:
Spring planting conditions throughout Iowa were cold and wet, and most soybean fields were planted later to accommodate corn planting. June turned exceptionally dry, particularly in southern Iowa. The average monthly precipitation for the state of Iowa in June from 1893–2016 is 4.58 inches, but Iowa received an average of 3.6 inches in June 2017. Conditions remained dry until mid-August.
Soybean aphids arrived on soybean in mid-June, as they normally do in the northeastern Iowa. Hot and dry conditions in June favored twospotted spider mite colonization, particularly in southern counties. But as moisture stress subsided throughout Iowa, spider mite populations faded and soybean aphid colonization expanded. Some commercial fields experienced exponential growth of soybean aphid after bloom, especially in northern Iowa. In August, some 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. In some research trials near Sutherland, Iowa, poor knockdown with lambda-cyhalothrin was noted.

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.

View uploaded report Word file

Final Project Results

Updated September 27, 2018:
Spring planting conditions throughout Iowa were first cold and wet, and most soybean fields were planted later to accommodate corn planting. Then May was warmer than normal and June turned exceptionally wet throughout most of 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.

In addition to soybean aphid, Japanese beetle, bean leaf beetle and soybean gall midge were prevalent in some Iowa soybean fields. We conducted a “on the fly” efficacy evaluation at the ISU Johnson Research Farm and hope to have yield data summarized for the next reporting cycle.

I was able to complete proposed work, including research and extension related to soybean aphid management. I established a foliar insecticide efficacy evaluation at two locations in 2018 (northwest and northeast Iowa). I had 25+ treatments at each location. My extension efforts are summarized here:

View uploaded report Word file

View uploaded report 2 Word file

Treatment Recommendations. 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.

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

Outcomes: Soybean aphid is a significant economic pest. Depending on the severity and size of the field, they can be overlooked in some growing seasons in Iowa. Overall, participants attending the workshop did increase their understanding of SBA identification, scouting and management recommendations. Implementation of these tactics will lead to better crop protection and ultimately higher profits on the farm.

• Understanding SBA life cycle and biology had a 1,100% percent increase.
• Knowing SBA host plant resistance options had a 900% percent increase.
• Awareness of SBA insecticide resistance had a 700% percent increase.
• Implementing integrated SBA management had a 1,000% percent increase.

Participants were asked about their perception of value, and 100% said it was a “very valuable” workshop. There were notable behavior changes indicated in the survey summary: 58% said they will consult with ISU regarding future pest management decisions; 44% said they will scout and use economic thresholds for SBA. In general, respondents indicated the four speakers contributed to a successful workshop. For example, 93% of people attending the workshop said Erin Hodgson had “excellent” energy, and 100% of people said Erin had “excellent” engagement with the group and were experts in their respective fields.

Impact Statement: Soybean is an important crop in Iowa, with nearly 10 million acres and production value of over $5.3 billion in 2016. Pest resistance in soybean is a critical issue in Iowa. Soybean aphid are becoming resistant to conventional management tactics. The participants showed a large increase in understanding of the emerging resistance issues, scouting and implementing integrated approaches for crop protection. If workshop participants use the information learned to help Iowa soybean farmers better manage SBA through integrated approaches, as they indicated they would, reduced yield losses from this high-profile soybean pests would be significant because of the pests’ widespread distributions among the 10 million acres of soybeans currently grown in the state.

Project Years