Soybean production in Minnesota is now threatened by multiple invasive insect pests. The soybean aphid (Aphis glycines), continues to be the most damaging insect pest of soybean. However, the Japanese beetle (Popillia japonica), is spreading and causing increasing injury to soybean. Growers need information about how co-occurring insect pests affect soybean yield to make better informed management decisions. The Koch lab has advanced drone-based scouting for soybean aphid, but we must understand how co-infestation by other insects like Japanese beetle affect spectral reflectance of soybean canopies. The work proposed here will continue (third year of a three-year project) our evaluation of the impact of combined infestation by these pests on soybean yield, quality and spectral reflectance of the soybean canopy. Results of this research will be disseminated to growers and stakeholders through active Extension programming. Overall, this project aligns well with the grower assessed priority areas and results will contribute to greater economic and environmental sustainability of soybean production.

The project proposed here aligns well with the mission statement of the MSR&PC Production Action Team and specifically addresses the following “Grower Assessed Priority Areas”:
1. “Soybean farmers need continued research into cultural, chemical and biological control mechanisms for management of soybean insects…” (soybean aphid management could be improved through improved efficiency in scouting via remote sensing)
2. “Soybean Farmers need integrated pest management strategies that deal with new or acute infestations of insect pests…” (Japanese is a new invasive insect affecting MN agriculture)
Background: The soybean aphid (Aphis glycines), continues to be the most damaging insect pest of soybean. However, the Japanese beetle (Popillia japonica), another invasive species from Asia, is spreading and causing increasing injury to soybean. Japanese beetle is an emerging crop pest concern across the region. These two pests now co-occur in soybean fields in southern Minnesota, but it remains unknown how their combined injury affects soybean. Without this knowledge, growers are unable to make fully informed manage decisions. Growers could be unnecessarily increasing insecticide inputs or incurring yield losses due to damaging infestations not being treated appropriately. Likewise, it is unclear how Japanese beetle feeding could affect efforts to use drone-based scouting for soybean aphid. The aim of this project is to improve the sustainability of soybean production by advancing management recommendations for combined infestations of soybean aphid and Japanese beetle.

• Objective 1: Assessing combined effects of Japanese beetle and soybean aphid on soybean
o Goal 1: Determine combined effects of Japanese beetle and soybean aphid on soybean yield and quality
o Goal 2: Determine effects of Japanese beetle feeding alone and in conjunction with soybean aphid on plant spectral reflectance
Objective 1: Assessing combined effects of Japanese beetle and soybean aphid on soybean. (Koch, Ribeiro, Behnken & Miller)
Justification:
This objective will improve management of and scouting for combined infestations of soybean aphid and Japanese beetle in soybean fields. The first component of this objective will quantify the effects of combined infestation of soybean aphid and Japanese beetle on soybean yield and quality. These results will inform management recommendations (treatment thresholds) to ensure these pests are being optimally managed. Thresholds exist for determining when to apply insecticides for either of these pests alone, but research-based recommendations are lacking for management of combined infestation by these pests. Research in other crops indicates combined attack by two or more different insect pests may result in additive (impact to the plant equal to sum of impacts from individual pests), synergistic (impact to the plant greater than sum of impacts from individual pests) or antagonistic (impact to the plant less than sum of impacts from individual pests) effects on the crop. Because the interactions between soybean and these two insects remain unknown, growers may be making incorrect decisions for management of these pests, such as: 1. applying insecticide when not necessary (wasted input costs) or not applying insecticide when it would have been necessary (lost yield due to unmitigated pest injury). Therefore, research is needed to characterize the combined effects of Japanese beetle and soybean aphid on soybean yield, which will provide a research-based foundation to improve management of these two pests.
The second objective will characterize the effects of soybean aphid and Japanese beetle feeding individually and combined on plant spectral reflectance to increase the accuracy of drone-based remote sensing for soybean insect pests. Previous work from the Koch lab has shown potential for use of drones to scout for soybean aphid. This new technology could reduce the time and effort needed to scout for aphids. However, the potential confounding impact of other stressors, such as Japanese beetle, on remotely sensed spectral data need to be understood.
Methods:
Experimental plots will be established in two locations in southern Minnesota where soybean aphid and Japanese beetle are likely to occur. We will use a randomized complete block design to test the effects of soybean aphids and Japanese beetle on soybean yield and spectral reflectance of the soybean canopy. Experiments will comprise 4-6 replications of up to 4 treatments (1. no pests, 2. soybean aphid infestation, 3. Japanese beetle infestation, and 4. combined infestation of both pests). Insect populations will be manipulated through use of cages over plants and/or insecticides. On a regular basis, data on soybean aphid abundance will be collected through counts of aphids on plants and data on feeding by Japanese beetle will be collected through estimates of defoliation. Yield data for each plot will be collected at the end of the season. Ground-based hyperspectral data will also be collected on a regular basis throughout the growing season. Regression and ANOVA analyses will be performed to determine the effects of soybean aphid, Japanese beetle and their interaction on soybean yield, quality and canopy hyperspectral reflectance.

Results of this research will be disseminated through a multi-media outreach effort. Dr. Koch and collaborators have extension responsibilities and interact with growers and agricultural professionals (crop consultants, industry and agency staff, etc.). We can leverage Extension’s large, integrated outreach system, which is well-suited for the distribution of agricultural information. An example is field days held at research and outreach centers, at which we will present results of this research. Furthermore, results of the project proposed here will be delivered at agricultural professional and producer meetings during winter months, and published on Extension’s crop news blog. Research results will be presented at scientific conferences and published in peer-reviewed scientific journals, which will provide scientific validity to the research. Specific funding is requested to: 1. Print and disseminate publication on insecticide resistance management; and 2. Produce and disseminate video on insecticide resistance management

Update:
Proposal title: Soybean insect management (2021): Soybean aphid and Japanese beetle
Reporting period: 1 May 2021 to 30 November 2021

Proposal Objectives & Goal Statements:
• Objective 1: Assessing combined effects of Japanese beetle and soybean aphid on soybean
o Goal 1: Determine combined effects of Japanese beetle and soybean aphid on soybean yield and quality
o Goal 2: Determine effects of Japanese beetle feeding alone and in conjunction with soybean aphid on plant spectral reflectance

Specific project achievements during this reporting period:
Objective 1: Experimental plots were set up in the field in St. Paul, Rosemount and Rochester, MN. In St. Paul and Rosemount, cages were used to manipulate pressure from aphids and Japanese beetles. In addition, an artificial defoliation treatment was included in St. Paul. In Rochester cages could not be used so we relied on ambient levels of aphids and beetles. However, the drought conditions adversely affected populations of both insects, so the experiment could not be completed at Rochester. Per plant aphid counts, visual defoliation, computer calculated defoliation, and hyperspectral measurements were taken of all plots over multiple weeks at each site. At crop maturity, we harvested the plots from St. Paul. While sampling the plots in St. Paul and Rosemount, we observed injury (leafmines) that we had not previously seen on soybean. We determined these were a new species feeding on soybean and published a paper documenting this and discussing its implications for soybean. The insect causing the leafmines is the caterpillar of a tiny moth called Macrosaccus morrisella.

Objective 1, Goal 1: Yield and quality data will be analyzed this winter.

Objective 1, Goal 2: Hyperspectral data collected from field plots will be processed and analyzed this winter.

Challenges encountered
Ambient levels of soybean aphid and Japanese beetle were extremely low in Rochester, due to the drought conditions. Therefore, we were unable to collect data from this location.

Dissemination of data/information during this reporting period
Results of this research and relevant information will be disseminated in presentations and print. The reports of the new leafmining insect were published here: https://doi.org/10.1093/jipm/pmab038

Update:

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