Database Research SummariesSoybean Entomology in the North Central Region: Management and Outreach for New and Existing Pests
Research Focus
Soybean insect pests not only reduce yield, but can also reduce grain quality and alter oil and protein content. In addition, inefficient pest management adds to the expense of farm production, cutting into farmers’ bottom lines.
This project involves 24 researchers in all 12 states of the North Central region: South Dakota, North Dakota, Minnesota, Wisconsin, Michigan, Indiana, Ohio, Illinois, Iowa, Nebraska, Kansas, and Missouri. Our four main program areas are (1) extension and outreach; (2) insect management; (3) aphid-resistant varieties and (4) insect monitoring.
The objectives within these programs address the efficient, cost-effective management of defoliating (chewing) insects, the role of cover crops relative to insects in soybean production, and the ability of honey bees to improve soybean yield. The team has made significant advances in incorporating native aphid-resistance genes into high-yielding soybean lines, and has forged a public-private partnership with Pioneer Hi-Bred International, now Corteva AgriScience, to advance aphid-resistant soybean varieties for wide-scale commercialization.
The soybean team in this project is multi-disciplinary, with researchers in the fields of entomology, agronomy, and plant breeding. Several of our objectives are coordinated multi-state efforts making our results applicable to a broad geographic area and creating greater research efficiencies through collaboration.
Objectives
Extension/Outreach and Farmer Feedback
- Extension coordination and deliverables
- Determining farmer needs and priorities
Insect Management and Profitability
- Management guidelines for defoliating insects
- Cover crops: insects in cereal rye to soybean transition systems
- Pollinators to improve soybean yield
- Insecticide-resistant soybean aphids
Aphid-Resistant Varieties and Aphid Virulence Management
- Advancing aphid resistant soybeans through a public-private partnership
- Soybean breeding for aphid resistance
Insect Monitoring
- Biological control of soybean aphid
- Monitoring soybean aphids and other soybean insect pests in suction traps
Results
Extension/Outreach and Farmer Feedback
The popular field guide Stink Bugs of the North Central Region is in it’s second printing. The Management of Insecticide-resistant Soybean Aphids fact sheet was updated in September 2019. The second edition of the Soybean Aphid Field Guide and Effectiveness of Neonicotinoid Seed Treatments in Soybean continue to be popular publications. We completed a draft of an extension publication detailing the pollinators found in North Central soybean fields.
Insect Management and Profitability
Defoliation:Â We have developed a defoliation sampling protocol for use during our first field season on this project (summer 2019). Sampling was conducted on commercial fields or large production areas on research farms; fields with insect defoliation were identified during the season in six states.
Pollinators: Participants in ND, SD, IA, OH, MN, NE, IN, MO, WI collected pollinators in soybean fields in Year 1 of the project. We were positively surprised by the overall bee and syrphid fly species richness and abundance in the 108 bee species in 27 genera from five families, and 11 syrphid fly species in six genera indicate that syrphid flies and especially bees can be relatively abundant and diverse in soybean fields, a monoculture environment. Our results provide baseline data on the bee and syrphid fly fauna associated with flowering soybean in Midwest.
We are currently assessing the diurnal activity of wild and managed bees in soybeans. Knowing the time of day when pollinators are most active in soybean can help producers make decisions about when to spray.
Cover crops: We have completed the first year of a 3-year study in which 14 locations in 7 states were planted to wheat or rye cover crops. Cover crops are planted between mid-June and mid-November at a seeding rate of 58 to 113 lb./acre. Herbicide applications to terminate cover crops begins in April. Data collection on insect damage begins in early summer 2019. This study will be repeated in Year 2 and 3 of the project.
Aphid-Resistant Varieties and Aphid Virulence Management
Breeding for resistance: The breeding program continues to develop high-yielding lines that have the native resistance genes Rag1 and Rag2 stacked together. The program recently licensed a variety with this two-gene stack to a seed company located in Iowa and there is interest from other companies to license additional lines with this stack.
We have also successfully incorporated 5 Rag genes singly and in combinations to combat different aphid biotypes. We achieved this over the past 6 months, by developing experimental lines in a maturity group (MG) I and a MG II background that have all 32 combinations of homozygotes (same gene from both parents) for resistance and susceptible alleles at Rag1, Rag2, Rag3, Rag4, and Rag6. All five genes were backcrossed into both backgrounds and combined into an F1 that was heterozygous for the five genes.
From October to January, F2 plants segregating for the five genes were grown in a greenhouse and plants were selected that contained different combinations of the genes. In January, F3 progeny from each selected F2 plant were grown and among the F3 progeny, plants homozygous for all five gene were selected. We were successful in selecting all 32 combinations of homozygous plants for both backgrounds except in one case the selected plant was still heterozygous for one gene.
During the summer, F3:4 lines from each combination will be grown in the field to increase seed that can be used for genetic studies. In the one case that homozygosity for all five genes was not achieved, we will select homozygous plants for the line. Plants were harvested this fall, and we should be able to provide seed of lines with these combinations to researchers.
Aphid virulence management for resistant varieties:Â We have found that aphid-resistant soybeans blended with aphid-susceptible plants can serve as a refuge while still being effective for suppressing aphids in the field. Thus, “refuge-in-a-bag” could be a viable resistance management strategy for the sustainable use of soybean aphid resistant soybeans.
Insect Monitoring
The 2019 sampling for mummies of Aphelinus (a common hyperparasite of the soybean aphid) in soybean is complete. Collaborators sampled 3 times, in late June, July, and August, and mailed those samples to Saint Paul, MN. Last year we found aphids in all states but Missouri and Nebraska, and we found Aphelinus in the Dakotas, Minnesota, Wisconsin, Michigan and Ohio. We are also tracking 7 hyperparasitoids from 4 genera.
The suction trap data were also posted to https://suctiontrapnetwork.org/data/. This public website allows users to select any suction trap location and see a graph of the seasonal abundance for the eight most abundant aphid species.
Importance
- Coordinated, collaborative research and outreach is the most efficient way to address insect pest problems that affect production and profitability.
- Farmers will benefit from the unbiased and current information in new Extension and outreach publications, including the second edition of the Soybean Aphid Field Guide.
- Soybean varieties with multiple genes for aphid resistance have been developed and released, providing farmers with an effective, low-cost control strategy.
- To preserve the efficacy of resistant varieties, a strategy of blending aphid-resistant soybeans with aphid-susceptible plants (“refuge-in-a-bag”) is being developed for farmers. This combination would serve as a refuge while still being effective for suppressing aphids in the field.
- Farmers can have a new understanding that pollinators such as syrphid flies and especially bees can be relatively abundant and diverse in soybean fields. Knowing the time of day when pollinators are most active in soybean help producers make decisions about when to spray.
- A new understanding of aphid insecticide resistance will help growers preserve the efficacy of this control tactic. See Management of Insecticide-resistant Soybean Aphids.
For more information about this research project, please visit the National Soybean Checkoff Research Database.
Funded in part by the soybean checkoff.
