The Issue
The soybean aphid is the most significant insect pest of soybean production, especially in Minnesota. The number of soybean acres treated with broad-spectrum insecticides has increased dramatically since the invasion of the soybean aphid in 2000, which threatens the economic and environmental sustainability of soybean production. Growers need more economically and environmentally efficient options to protect their yield.
Key Activities
Since 2016, the Minnesota Invasive Plants and Pests Center has helped fund a team of research and Extension soybean specialists to explore two ways to help Minnesota soybean farmers:
- Developing Aphid-Resistant Soybeans: Pest-resistant crop varieties offer one alternative to heavy insecticide use. At least nine soybean aphid-resistance genes have been identified, but few of today’s commercially available resistant varieties are suitable for Minnesota. UMN researchers are thus looking to close that gap for local growers by developing a selection of early maturing soybean aphid-resistant lines appropriate for Minnesota. They are using the USDA Soybean Germplasm Collection, which has become an important reservoir of genetic diversity, to zero in on soybean lines that contain soybean aphid-resistance genes called Rag — ‘resistant to Aphis glycines.’ These Rag genes will then serve as building blocks for breeding aphid-resistant lines in Minnesota.
- Using Drone Technology to Help with Pest Scouting: The time-intensive nature of traditional pest scouting has led some growers to bypass it, applying broad-spectrum insecticides preventively regardless of aphid density. Fortunately, unmanned aerial vehicles (UAVs) show promise as a more convenient option for estimating pest damage and insect counts across a field. Previous research had shown spectral reflectance of soybean canopies caused by aphid-induced stress could be detected from ground-based sensors; however, it remained unknown whether these changes could also be detected from UAV-based sensors. The team set up small-plot trials where cages were used to manipulate aphid populations. Additional open-field trials were then conducted, where insecticides were used to create a gradient of aphid pressure. Whole-plant soybean aphid densities were recorded along with UAV-based multispectral imagery. Simple linear regressions were used in determining whether UAV-based multispectral reflectance was associated with aphid populations.
Results
To date, one soybean line with aphid resistance has been developed and commercialized with Viking Seeds in Albert Lea, Minn. (Viking 0.0654AT). Nine additional lines are in advanced stages of testing. However, concerns persist that aphids could quickly adapt to resistance in the plant. Thus, the team is also exploring ‘stacking’ of multiple resistance genes to create a stronger, more robust resistance and also expanding their work to include food-type soybean germplasm.
Drone trial findings showed near-infrared reflectance decreased with increasing soybean aphid populations in caged trials when cumulative aphid days surpassed the economic injury level, and in open-field trials when soybean aphid populations were above the economic threshold (250 aphids per plant and/or over 80 percent of plants infested). These findings provide the first documentation of soybean aphid-induced stress being detected from UAV-based multispectral imagery and advance the use of UAVs for remote scouting of soybean aphid and other field crop pests.
The team is now working with UMN Extension to incorporate their findings into a patent-pending tool for decision-making about insecticide applications for soybean aphid to a broadly applicable, satellite-based platform. This tool could then help prioritize fields for ground- or drone-based scouting, or even enable decision making for individual fields.
Public Value
Soybeans make up 30 percent of Minnesota’s total agricultural exports and remain the state’s top export commodity. In addition, the state ranked third in the nation for soybean production as of 2019. This research directly serves the agricultural community of Minnesota by advancing the development of aphid-resistant soybean cultivars and improving remote sensing technologies to locate damaging levels of soybean aphids. The resulting decreases in insecticide inputs will reduce adverse economic and environmental impacts of soybean aphid management and will be especially beneficial economically to organic producers who have few options for aphid management.