This proposed 3-year project would continue to evaluate planting date relative to adult emergence and expand this effort to include the use of an insecticide seed treatment. In addition, growers would be identified to evaluate and compare the results of planting dates on their farm relative to soybean gall midge emergence. Results from this study would provide farmers with an understanding of risk for overwintering soybean gall midge infestation with different planting dates as well as the potential for seed treatments to mitigate early season infestations.

The first objective will be to evaluate soybean gall midge infestation and injury of soybean planted at four different planting dates with and without an insecticide seed treatment.
For the second portion of the project, farmer fields will be monitored for adult emergence data as part of an ongoing NCSRP and NSB project. To add to this project, adjacent farmer fields will be evaluated for the planting date and the use of seed treatments relative to adult emergence at these sites.

For the planting date and insecticide study, a research site will be located in fields adjacent to areas with significant soybean gall midge pressure the previous year. The first objective will be to evaluate soybean gall midge infestation and injury of soybean planted at four different planting dates with and without an insecticide seed treatment. Soybean will be planted in 10x30 ft. plots at a population of 140,000 plants per acre in a split-plot randomized complete block design with a minimum of 4 replications. Split-plot treatments would consist of soybean seed with and without an insecticide seed treatment at a labeled rate. Insecticide seed treatment will be chosen based on the most effective product identified from industry-funded university trials over two years of data. Planting dates will start on April 15th with plantings occurring every two weeks until June 1st, for a total of four planting dates. Overwintering adults will be tracked using emergence cages in an adjacent source field. In addition, 1st and 2nd generation adult emergence will be monitored from the non-yield rows of the planting date study. Plots will be evaluated 2-3 weeks after adult emergence to determine the percentage of infested plants and assigned an injury score based on the number of dead or dying plants. Additional evaluations would be made 2-3 weeks after each adult flight. Plant development stage will be recorded every week following emergence and yields will be taken on plots at the end of the growing season.

For the second portion of the project, farmer fields will be monitored for adult emergence data as part of an ongoing NCSRP and NSB project. To add to this project, adjacent farmer fields will be evaluated for the planting date and the use of seed treatments relative to adult emergence at these sites. These adjacent fields will be evaluated using the same methods described in the first experiment. Hand harvests will be made on these adjacent fields at the end of the season.

Updated May 19, 2023:

View uploaded report

Such results highlight the importance of delayed planting. Our data also indicated there may be planting dates that are highly susceptible to injury from soybean gall midge. Growers looking to potentially reduce soybean gall midge populations for future years may want to consider delayed planting if they have significant historical injury and pressure from soybean gall midge. Seed treatment impacts were limited to soybean plantings from April 22nd to May 12th. Our results indicate that planting date alone is more effective but more research is needed.

Planting date has always been an important consideration for soybean farmers. Knowledge of the impact on this tactic with significant soybean gall midge pressure would allow farmers to potentially prioritize fields to reduce risk of soybean gall midge injury. Studies of its interaction with seed treatments would provide an evaluation of the value of this tactic in combination with planting date to mitigate losses and maintain production of soybean.