Project Details:

Evaluation plant pest interactions to optimize soybean yield

Parent Project: This is the first year of this project.
Checkoff Organization:Iowa Soybean Association
Categories:Insects and pests, Crop management systems
Organization Project Code:
Project Year:2013
Lead Principal Investigator:Erin Hodgson (Iowa State University)
Co-Principal Investigators:
Aaron Gassmann (Iowa State University)
Gregory Tylka (Iowa State University)
Keywords: Best Management Practices, Soybean Aphid, Soybean Cyst Nematode (SCN), Soybean Disease Management, Soybean Educational Activities

Contributing Organizations

Funding Institutions

Information and Results

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Project Summary

With the advent of new seed treatment management products and resistance of soybean varieties, there is a need to evaluate the interactions of these management tactics with soybean aphids and soybean cyst nematode infested fields. There is interest in understanding the effects of these management tactics on naturally occurring soil-borne organisms which may play a critical role in keeping pest population densities in check.

Project Objectives

1. Determine optimum yield potential using combinations of pest management tactics.
2. Evaluate interactions among host plant resistance, pesticides and pests to optimize yield.
3. Conduct greenhouse experiments to measure treatment effects on pest-killing pathogens and key soybean pests.
4. Promote optimal yield recommendations with multiple pest suppression tactics.

Project Deliverables

Progress of Work

Two field locations were established for this project in 2013 and throughout the summer extensive field work was carried out at both locations. Aphid counts were carried out weekly at both locations until aphid numbers significantly dropped in early September.

Cumulative aphid day (CAD) data was calculated for the small field plots in order to measure seasonal aphid exposure on our different soybean varieties as well as the different seed treatments.

Nashua had greater aphid pressure than Woodruff throughout the 2013 growing season. Because the average aphids/plant never reached the threshold of 250 prior to the R5 stage of the soybeans, we did not apply Warrior II insecticide to plots designated to receive insecticides.

Final Project Results

During the summers of 2013-2015, two field locations were established each year. Plots were set up in a randomized complete block design with eight replications, including four soybean varieties (susceptible, SBA resistant, SCN resistant, and SBA+SCN resistant), and three seed treatments (naked, ApronMaxx, Avicta Complete). Soybean aphid (SBA) populations were monitored during the summer and cumulative aphid days were estimated for each treatment. Soybean cyst nematode (SCN) eggs were sampled at planting and harvest.

Results of the 3-year study:
• SBA- and SCN-resistant varieties support lower populations of aphids and nematodes, respectively.
• SCN-resistant varieties yield higher than SCN-susceptible varieties.
• Seed treatments did not consistently improve yields, even with SBA- and SCN-susceptible varieties

Conclusions of the 3-year study:
• SBA resistance (Rag genes) is an effective suppression tool and may reduce the reliance on foliar insecticides.
• SBA-resistant variety breeding needs to improve yield potential.
• SCN resistance (PI88788) reduces SCN populations and is an important consideration for variety selection.
• Using host plant resistance with seed treatments did not consistently produce higher yields.
• Prophylactic use of pesticidal seed treatments may not provide higher soybean yields, particularly on host plant resistance soybean varieties.

Benefit to Soybean Farmers

Performance Metrics

Project Years