Soybean Fungicide Trials, 2021

Soybean Fungicide Trials, 2021

Editor’s note: Data from 2021 is presented here since 2022 trials are not yet harvested. 2022 results will be posted to the Agronomy News Blog.

Trials were established at the Wye Research and Education Center in Queenstown, MD (WYE) and the Western Maryland Research and Education Center (WMREC) in Keedysville, MD in 2021 to assess the efficacy of select fungicides for the suppression of foliar diseases of soybean. Soybean ‘MAS3720 E3/STS’ were no-till direct-seeded into soybean residue at 150,000 seeds/A on 18 May (WYE) and 26 April (WMREC) using a 10-foot no-till drill set on 7.5 inch row spacing. Plots were 30 feet long and established in a randomized complete block design with 5 replications and data collection occurred from the center 5 feet of each plot. Soybean cultivation practices were consistent with recommendations from the University of Maryland Extension. The trial consisted of seven foliar fungicide treatments and a non-treated control. Fungicide applications were applied with a backpack CO2 sprayer with TeeJet 8003 nozzles calibrated to deliver 20 GPA at 35 psi to the center 80 inches of each plot. Fungicides were applied at the R3 growth stage. Treatments with subsequent applications were made 14 days later. Based on the disease history of these fields and monoculture soybean rotation, natural pathogen inoculum levels were utilized for disease infection. Disease severity from frogeye leaf spot (FGL; Cercospora sojina) was visually rated as the percent leaf area infected in the upper canopy from the center four rows of each plot at the R6 growth stage. Normalized Difference Vegetation Index (NDVI) ratings were collected between R6-R7 using a handheld Greenseeker® from the center rows of each plot. Yields were collected by harvesting the center 5 feet of each plot and data reported are adjusted to 13% moisture. Plots were harvested on 23 Nov at WYE and November 24 at WMREC. Seed quality ratings were recorded at WMREC due to the presence of Diaprothe spp. (stem canker), which can also infect seeds. A random sample of 100 seeds were collected from each plot and the number of discolored seeds was recorded. Data were analyzed using ANOVA and significant differences between treatments were separated using Fisher’s Least Significant LSD (LSD; α=0.10).

Growing conditions were generally favorable, especially at WYE, and we did not observe any ratable foliar fungal diseases. This is likely due to the weather conditions around pod fill, as well as the resistance package in the soybean variety; frogeye leafspot resistance rating of 8 on a 10-point scale (10 being the most resistant). Yields were exceptional at WYE and slightly above average at WMREC, with an average overall trial yield of 94.5 bushels per acre and 57.9, respectively. None of the treatments differed from the mean at either location. Miravis Top, Revytek, and Veltyma improved seed quality of Diaporthe-infected grain at WMREC. No phytotoxicity was observed with any of the fungicide treatments. All fungicide treatments, with the exception of Headline, significantly increased incidence of green stem compared to the non-treated control.

This research was funded by the Maryland Soybean Board. Special thanks to the Maryland Agriculture Experiment Station and the farm crew at the WMREC and WYE.

ᶻ Means followed by the same letter are not significantly different based on Fisher’s Least Significant Difference (LSD; α=0.10).

This article appears in November 2022, Volume 13, Issue 8 of the Agronomy news.