The soybean tentiform leafminer is a native insect that has recently developed the ability to feed on soybean. The levels of leaf injury caused by this pest are alarming and could threaten soybean yields. Therefore, urgent work is needed to evaluate potential control methods for this pest. The work proposed here is the second year of a three-year project focused on evaluating control methods that could be used to respond to this pest. First, certain insecticides with translaminar activity (ability to move through leaves) proved effective at controlling this pest in the first year of this project. Further work is needed in this second year to evaluate additional insecticides, particularly those with the ability to move through leaves to contact the insects inside the mines. This field efficacy trial will be performed in the field of a cooperating farmer. Second, leafmining insects are generally attacked and killed by multiple parasitic wasps, and our preliminary work has found that the soybean tentiform leafminer is attacked by several species of parasitic wasps. However, further work is needed in this second year to characterize the community of parasitic wasps attacking this pest and quantify the levels of mortality they inflict on the pest populations. Results of this proposed work will allow us to develop integrated pest management recommendations including chemical and biological controls for this pest.

1. GOAL: To build the foundation for the development of management programs for soybean tentiform leafminer, we propose the following goals and objectives:
OBJECTIVES:
1. Evaluate the efficacy of insecticides against soybean tentiform leafminer in soybean fields
2. Assess diversity and impacts of parasitic wasps attacking soybean tentiform leafminer populations

This project will provide several important deliverables that will advance management programs for
soybean tentiform leafminer in Minnesota. This project will produce foundational knowledge on
chemical and biological control against this pest. This knowledge will help farmers determine which
insecticides to use against this pest and if natural control provided by parasitic wasps can help suppress
infestations. This knowledge will be housed on the UMN Extension website and made widely available
to farmers and the agricultural community through our extension programming (see communication
plan above) and through the communication channels of Minnesota Soybean. Finally, this project will
facilitate the continued training of post-doctoral in Entomology, who will gain expertise in pest ecology
and integrated pest management.

Updated August 30, 2024:
Reporting period: 1 May 2024 to 30 July 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: Evaluate the efficacy of insecticides against soybean tentiform leafminer in soybean fields
Goal 2: Assess diversity and impacts of parasitic wasps attacking soybean tentiform leafminer populations

Specific project achievements during this reporting period:
Goal 1:
For the field insecticide efficacy experiment, we identified a soybean field with an STL infestation in south-central Minnesota and attained permission to perform this work. Research plots have been established in a randomized complete block design. Preparations are being made to apply insecticides to the plots in August.
Goal 2:
To characterize the community of parasitic wasps attacking STL and the magnitude of their impact on this pest, we identified two soybean fields with nearby wooded areas containing hogpeanut. These fields are located on the St. Paul Campus of the UMN and on a farm in south-central Minnesota. Since early vegetative growth stages of the soybean plants, the soybean and hogpeanut plants have been sampled to quantify the level of STL infestation and to collect infested plant tissue for rearing of parasitic wasps in the laboratory. The wasps emerging from infested plant tissue in the laboratory are being preserved for later identification. The communities of parasitoids and their impacts on the pest will be compared between plant types and locations.

Challenges encountered
No problems occurred during this period

Dissemination of data/information during this reporting period
Results of this work will be disseminated to stakeholders in winter extension meetings.

Updated November 25, 2024:
Reporting period: 1 August 2024 to 31 October 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: Evaluate the efficacy of insecticides against soybean tentiform leafminer in soybean fields
Goal 2: Assess diversity and impacts of parasitic wasps attacking soybean tentiform leafminer populations

Specific project achievements during this reporting period:

Goal 1:
A field insecticide efficacy experiment was performed in an infested soybean field on a farm near Henderson, MN. Research plots were established in a randomized complete block design parallel to the edge of the field to account for this insect’s strong edge effect in infestations. The plots were sprayed with insecticides on August 19 and leaves were collected after 1, 2 and 3 weeks to compare the leaf area mined (injured) and survival of larvae in the leaf mines in the plots treated with the various treatments (insecticides and untreated control). Data from this experiment will be summarized and analyzed in the next reporting period.

Goal 2:
To characterize the community of parasitic wasps attacking STL and the magnitude of their impact on this pest, we sampled two soybean fields and corresponding nearby wooded areas containing hogpeanut. These fields and wooded areas were located in St. Paul and on a farm near Henderson. Sampling began during early vegetative growth stages of the soybean plants and continued through plant maturity. On each sample date, we collected infested soybean and hogpeanut leaves to quantify the level of STL infestation and to rear insects (adult STL and parasitic wasps) from the infested leaves in the laboratory. The wasps that emerged from infested plant tissue in the laboratory were preserved and will be identified in the next reporting period. The resulting data will be analyzed in a future reporting period, to compare the communities of parasitic wasps and their impacts on the pest between plant types and locations.

Challenges encountered
No problems occurred during this period

Dissemination of data/information during this reporting period
Results of this work will be disseminated to stakeholders in winter extension meetings.

Soybean tentiform leafminer is a new pest that poses a threat to soybean production. Currently,
knowledge about this pest in soybean is limited and little is known about potential management tactics.
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 how to effectively manage this pest.
More specifically, recommendations for chemical and biological controls will be generated to help the
farmers protect their crops.