2023
Evaluating control methods for a new leaf-mining pest of soybean in Minnesota
Category:
Sustainable Production
Keywords:
Biotic stressCrop protectionField management Pest
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Robert Koch, University of Minnesota
Co-Principal Investigators:
Project Code:
10-15-44-23163
Contributing Organization (Checkoff):
Leveraged Funding (Non-Checkoff):
No other funding has been secured for research on this pest. We will seek complementary funding from the Minnesota Rapid Agricultural Response to further evaluate the biology and interactions between M. morrisella and soybean plants, and additional management tactics.
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Institution Funded:
Brief Project Summary:
A native North American moth has been found in soybean fields in southern Minnesota and eastern South Dakota. The soybean tentiform leafminer is usually found in wooded areas, but has migrated to soybean fields. This project will assess effectiveness of several insecticides against the adult moth in the lab and in fields. The researchers will study to learn more of its lifecycle and soybean host preferences, as well as how many generations occur over a single soybean growing season through this project. Because it is new to soybeans, there has been very little research done on this tiny moth.
Key Beneficiaries:
#entomologists, #extension crop specialists, #farmers
Unique Keywords:
#insects and pests, #leafminer, #moth, #soybean pests
Information And Results
Project Summary

This project addresses a priority item listed under the category of Soybean Pest Management in the FY2023 request for proposals: ”Soybean farmers need continued research into cultural, chemical and biological control mechanisms for management of soybean insects including, but not limited to, soybean aphid, Japanese beetle and soybean gall midge.”

Macrosaccus morrisella (sometimes called the soybean tentiform leafminer) is a tiny moth native to North America. It was found attacking soybean in the United States for the first time in 2021 (Koch et al. 2021). The immature stage (larva) of this moth lives and feeds inside leaves (Davis and De Prins 2011), leading to loss of functional leaf area (i.e., defoliation). In 2022, M. morrisella was found infesting soybean across a broad area of southern Minnesota and eastern South Dakota, with some infestations causing up to 40% defoliation in parts of fields (Koch, unpublished data). Such levels of defoliation by insect pests can significantly decrease soybean yield (Owen et al. 2013).

The appearance of a leaf-mining insect like M. morrisella in Midwest soybean is a significant concern, especially because other leaf-mining moths are significant pests of soybean in other places, like the leaf-mining moth Aproaerema modicella in Africa, Asia, and Australia (Gaur and Mogalapu 2018, Buthelezi et al. 2021). Furthermore, the leaf-mining moth M. robiniella, a related species of M. morrisella, is a significant pest of ornamental plants in Europe (Davis and De Prins 2011). Thus, research is urgently needed to assess the potential impacts of M. morrisella and how to manage its infestations. Unfortunately, there is only limited knowledge on M. morrisella in the forest systems where it historically occurred in Eastern North America (Davis and De Prins 2011) and even less knowledge about it in soybean (Koch et al. 2021).

Project Objectives

To build the foundation for the development of management programs for M. morrisella, we propose the following goals and objectives:

Goal 1: Assess the effectiveness of insecticides for management of M. morrisella

• Objective 1: Evaluate the toxicity of insecticides against adults of M. morrisella in the laboratory
• Objective 2: Evaluate the efficacy of insecticides against M. morrisella in soybean fields

Goal 2: Assess host preference and varietal resistance of soybean to M. morrisella

• Objective 1: Determine host preference and varietal resistance of two native plants and several soybean varieties for M. morrisella
• Objective 2: Characterize relationship between abundance of M. morrisella in soybean fields and in native plants in wooded areas in close proximity

Project Deliverables

This project will provide several important deliverables that will advance M. morrisella management in Minnesota. This project will produce foundational knowledge on the chemical control, host preference and varietal resistance of soybean against M. morrisella. This knowledge will improve the general understanding of the biology of this pest and establish the foundation for the development of management. This knowledge will be housed on the UMN Extension website and made widely available to farmers and the agricultural community through our extension programming and through the communication channels of Minnesota Soybean. Finally, this project will facilitate the training of an undergraduate student in Entomology, who will gain expertise in pest ecology and integrated pest management.

Progress Of Work

Update:
Goal 1: Assess the effectiveness of insecticides for management of M. morrisella
• Objective 1: Evaluate the toxicity of insecticides against adults of M. morrisella in the laboratory
Bioassays were completed to evaluate the toxicity of Agri-Mek and Endigo against adults through oral, contact and oral+contact exposure routes. Data from this experiment are currently be summarized and analyzed.
• Objective 2: Evaluate the efficacy of insecticides against M. morrisella in soybean fields
A site to perform this experiment was identified near Henderson, MN. The insecticide application will occur in early to mid August.

Goal 2: Assess host preference and varietal resistance of soybean to M. morrisella
• Objective 1: Determine host preference and varietal resistance of two native plants and several soybean varieties for M. morrisella
Methodology was developed to evaluate the host range of this insect and seed were obtained for the experiment. Initial replications of the laboratory experiment comparing soybean, edamame and several other legumes were initiated in July and further replications will be conducted in August. Similar methods will be used for a comparison among soybean varieties and will be conducted in September and October.
• Objective 2: Characterize relationship between abundance of M. morrisella in soybean fields and in native plants in wooded areas in close proximity
Multiple locations around the state were identified for this sampling. Sampling was initiated during this reporting period and will likely continue into September.

Update:

View uploaded report Word file

Update:
Reporting period: 1 November 2023 to 30 January 2024

Proposal Objectives & Goal Statements:
To build the foundation for the development of management programs for soybean tentiform leafminer (STL), we propose the following goals and objectives:
Goal 1: Assess the effectiveness of insecticides for management of STL
• Objective 1: Evaluate the toxicity of insecticides against adults of STL in the laboratory
• Objective 2: Evaluate the efficacy of insecticides against STL in soybean fields
Goal 2: Assess host preference and varietal resistance of soybean to STL
• Objective 1: Determine host preference and varietal resistance of two native plants and several soybean varieties for STL
• Objective 2: Characterize relationship between abundance of STL in soybean fields and in native plants in wooded areas in close proximity

Specific project achievements during this reporting period:

Goal 1:
As previously reported, two experiments were performed to evaluate the toxicity of insecticides against STL. A laboratory bioassay showed that Agri-Mek and Endigo were toxic to STL adults through oral, contact and oral+contact exposure routes, with oral exposure being more toxic than contact exposure. In addition, a field insecticide efficacy experiment showed that Endigo provided better protection of the soybean canopy from STL than did Agri-Mek.

Goal 2:
The host preferences of STL were assessed in laboratory experiments. To assess the host range of STL, mated adults were allowed to oviposit for a defined period on different species of legume crop species (including soybean) in choice and no-choice settings. Across these experiments, STL show very strong preferences for soybean, with very few eggs being laid on any other legume crop species. Furthermore, the few eggs laid on legume crop species other than soybean did not develop to adults.
The potential for soybean varietal resistance to STL was assessed in laboratory choice and no-choice experiments. Mated adults were allowed to oviposit for a defined period on different genotypes of soybean including genotypes known to be resistant or susceptible to other pests, such as defoliators or aphids. This experiment is underway and will be reported on in the next progress report, but preliminary results suggest that some soybean genotypes with known resistance to other insects may also have resistance to STL.
To characterize the relationship between the abundance of STL in soybean fields and in native plants in wooded areas, multiple locations around the state were identified and sampled. Sampling was performed and results still need to be summarized and analyzed.

Challenges encountered
No problems occurred during this period

Dissemination of data/information during this reporting period

Scientific presentations:
Fuhr, F.M., A.V. Ribeiro, J.P. Menger and R.L. Koch. 2023, November. Lethal effects of insecticides against adults of Macrosaccus morrisella through multiple exposure routes. Meeting of the Entomological Society of America. National Harbor, MD.

Extension presentations:
Koch, RL. 2024, February. Biology and management of two new insect pests of soybean, soybean gall midge and soybean tentiform leafminer. Research Updates for Agricultural Professionals, Institute for Agricultural Professionals, University of Minnesota Extension. (30-minute presentation online with 55 attendees)
Ribeiro, A.V. and R.L. Koch. 2023, December. Evaluating control methods for a new leaf-mining pest of soybean in Minnesota. Prairie Grains Conference. Grand Forks, ND. (15-minute presentation with 30 attendees)

Final Project Results

Updated May 31, 2024:
Reporting period: May 1, 2023 to April 30, 2024

Proposal Objectives & Goal Statements:
To build the foundation for the development of management programs for soybean tentiform leafminer (STL), we propose the following goals and objectives:
Goal 1: Assess the effectiveness of insecticides for management of STL
• Objective 1: Evaluate the toxicity of insecticides against adults of STL in the laboratory
• Objective 2: Evaluate the efficacy of insecticides against STL in soybean fields
Goal 2: Assess host preference and varietal resistance of soybean to STL
• Objective 1: Determine host preference and varietal resistance of two native plants and several soybean varieties for STL
• Objective 2: Characterize relationship between abundance of STL in soybean fields and in native plants in wooded areas in close proximity

Specific project achievements during this reporting period:
Goal 1:
Studies with the insecticides Agri-Mek SC (abamectin) and Endigo ZXC (lambda-cyhalothrin + thiamethoxam) were developed with the objective to evaluate the effects against adults of M. morrisella through different routes of exposure; and the efficacy of field applications. In the experiment with adults, the survival of M. morrisella exposed to insecticides through oral exposure, or residual contact + oral exposure, was significantly lower than that for residual contact exposure alone, which in turn was lower than the untreated control. Within each exposure route, the response to the two insecticides did not differ. In the field experiment, at 21 days after insecticide application, the mean percentage of leaf area mined was significantly lower in plots treated with Endigo ZCX compared to plots treated with Agri-Mek SC or those left untreated. Taken together, these results suggest that Endigo ZXC and to a lesser extent Agri-Mek SC may have potential for management of M. morrisella.

Goal 2:
The threat posed by STL to other legume crops and the potential for host-plant resistance for management of this pest in soybean are currently unknown. Thus, complementary choice and no-choice experiments were carried out to assess the host range of STL among different species of legume crops and among different genotypes of soybean. STL was found to oviposit on its native host American hogpeanut and soybean (both grain and vegetable types), but not on red kidney bean, white kidney bean, cowpea, chickpea, fava bean, pea, and lentil. Low levels of oviposition were observed on mung bean and lima bean in a choice test, but no larvae of STL survived on either of those legumes. When soybean genotypes were compared, lower oviposition of STL was observed on the PI229358 and PI227687 in choice and no-choice oviposition tests, and lower survival rates of STL were observed on the PI229358 and M15-105140 in a no-choice test. Taken together, the results of this study indicate that the host range of STL appears to be restricted to the previously known native hosts and soybean, but continued monitoring for adaptation to other legumes is necessary. Furthermore, potential sources of soybean resistance against STL were identified and could be utilized in soybean breeding programs for development of host-plant resistance for management of this new soybean pest.

To characterize the relationship between the abundance of STL in soybean fields and in native plants in wooded areas, multiple locations around the state were identified and sampled. Sampling was performed and results still need to be summarized and analyzed.

Challenges encountered
No problems occurred during this period

Dissemination of data/information during this reporting period
Scientific presentations:
Koch, R.L., A.V. Ribeiro, J. Menger and F. Fuhr. 2024, March. What do we know about the biology and management of the soybean tentiform leafminer, a new pest of soybean? Meeting of the North Central Branch of the Entomological Society of America. Fort Collins, CO.
Koch, R.L. 2024, February. Biology and management of the soybean tentiform leafminer. 25-minute talk. Soybean Breeder’s Workshop, St. Louis, MO.
Fuhr, F.M., A.V. Ribeiro, J.P. Menger and R.L. Koch. 2023, November. Lethal effects of insecticides against adults of Macrosaccus morrisella through multiple exposure routes. Meeting of the Entomological Society of America. National Harbor, MD.

Scientific publications:
Führ, F.M., A.V. Ribeiro, J.P. Menger and R.L. Koch. Potential for chemical control of the soybean tentiform leafminer (Lepidoptera: Gracillariidae), a new pest of soybean. Journal of Economic Entomology (undereview with journal)

Extension presentations:
Koch, RL. 2024, February. Biology and management of two new insect pests of soybean, soybean gall midge and soybean tentiform leafminer. Research Updates for Agricultural Professionals, Institute for Agricultural Professionals, University of Minnesota Extension. (30-minute presentation online with 55 attendees)
Ribeiro, A.V. and R.L. Koch. 2023, December. Evaluating control methods for a new leaf-mining pest of soybean in Minnesota. Prairie Grains Conference. Grand Forks, ND. (15-minute presentation with 30 attendees)

Extension publications:
Ribeiro, A.V. and R.L. Koch. 2024. The soybean tentiform leafminer has been found in 51 counties in Minnesota, North Dakota and South Dakota. Minnesota Crop News, University of Minnesota Extension. January 9, 2024 https://blog-crop-news.extension.umn.edu/2024/01/the-soybean-tentiform-leafminer-has.html

Macrosaccus morrisella (soybean tentiform leafminer (STL)) is a tiny moth native to North America. It was found attacking soybean in the United States for the first time in 2021. The immature stage (larva) of this moth lives and feeds inside leaves, leading to loss of functional leaf area (i.e., defoliation). In 2022, STL was found infesting soybean across a broad area of southern Minnesota and eastern South Dakota, with some infestations causing up to 40% defoliation in parts of fields. Such levels of defoliation by insect pests can significantly decrease soybean yield.

The appearance of a leaf-mining insect like STL in Midwest soybean is a significant concern, especially because other leaf-mining moths are significant pests of soybean in other places, like the leaf-mining moth Aproaerema modicella in Africa, Asia, and Australia. Furthermore, the leaf-mining moth M. robiniella, a related species of M. morrisella, is a significant pest of ornamental plants in Europe. Thus, research is urgently needed to assess the potential impacts of STL and how to manage its infestations. Unfortunately, there is only limited knowledge on STL in the forest systems where it historically occurred in Eastern North America and even less knowledge about it in soybean.

To build the foundation for the development of management programs for STL, we pursued the following goals: 1: Assess the effectiveness of insecticides for management of M. morrisella; and 2. Assess host preference and varietal resistance of soybean to M. morrisella.

Studies with the insecticides Agri-Mek SC (abamectin) and Endigo ZXC (lambda-cyhalothrin + thiamethoxam) were developed with the objective to evaluate the effects against adults of M. morrisella through different routes of exposure; and the efficacy of field applications. In the experiment with adults, the survival of M. morrisella exposed to insecticides through oral exposure, or residual contact + oral exposure, was significantly lower than that for residual contact exposure alone, which in turn was lower than the untreated control. Within each exposure route, the response to the two insecticides did not differ. In the field experiment, at 21 days after insecticide application, the mean percentage of leaf area mined was significantly lower in plots treated with Endigo ZCX compared to plots treated with Agri-Mek SC or those left untreated. Taken together, these results suggest that Endigo ZXC and to a lesser extent Agri-Mek SC may have potential for management of M. morrisella.

The threat posed by STL to other legume crops and the potential for host-plant resistance for management of this pest in soybean are currently unknown. Thus, complementary choice and no-choice experiments were carried out to assess the host range of STL among different species of legume crops and among different genotypes of soybean. STL was found to oviposit on its native host American hogpeanut and soybean (both grain and vegetable types), but not on red kidney bean, white kidney bean, cowpea, chickpea, fava bean, pea, and lentil. Low levels of oviposition were observed on mung bean and lima bean in a choice test, but no larvae of STL survived on either of those legumes. When soybean genotypes were compared, lower oviposition of STL was observed on the PI229358 and PI227687 in choice and no-choice oviposition tests, and lower survival rates of STL were observed on the PI229358 and M15-105140 in a no-choice test. Taken together, the results of this study indicate that the host range of STL appears to be restricted to the previously known native hosts and soybean, but continued monitoring for adaptation to other legumes is necessary. Furthermore, potential sources of soybean resistance against STL were identified and could be utilized in soybean breeding programs for development of host-plant resistance for management of this new soybean pest.

Overall, this research provides a foundation for development of integrated pest management (IPM) programs for this new pest. The efficacy of some insecticides is understood and provides an “emergency response” tactic, if farmers need to protect yields from this pests feeding injury. This work also establishes a foundation for development of host plant resistance for this pest (pest resistant soybean), which offers a more sustainable longer term control. Future work will evaluate additional insecticides and biological control, as well soybean yield response to STL feeding for creation of more robust IPM program.

Benefit To Soybean Farmers

Macrosaccus morrisella is a new pest that might pose a significant threat to soybean production. Currently, knowledge about this pest in soybean is limited and the potential economic impacts to soybean production is unknown. This limits the ability of farmers to prepare for and respond to the pest. Investment in this project will enable us to provide recommendations to inform farmers about their risk for this pest. More specifically, recommendations for chemical and cultural control (i.e., varietal resistance) will be generated to help the farmers with actionable management tactics to protect their crops.

Indirectly, the proposed work rearing this insect in the laboratory should advance our abilities to maintain year-round colonies of this insect. Having the ability to produce M. morrisella in the laboratory year-round would advance all aspects of M. morrisella research and greatly increase the rate at which management recommendations are being developed to help farmers protect their crop from this pest.

The United Soybean Research Retention policy will display final reports with the project once completed but working files will be purged after three years. And financial information after seven years. All pertinent information is in the final report or if you want more information, please contact the project lead at your state soybean organization or principal investigator listed on the project.