2019
Determining Thresholds for Profitable Use of Fungicides to Control White Mold in Soybeans
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Contributor/Checkoff:
North Dakota Soybean Council
Category:
Sustainable Production
Keywords:
Crop protectionDiseaseField management
Parent Project:
This is the first year of this project.
Lead Principal Investigator:
Michael Wunsch, North Dakota State University
Co-Principal Investigators:
Project Code:
QSSB
Contributing Organization (Checkoff):
North Dakota Soybean Council
$16,062
Institution Funded:
North Dakota State University, Carrington Research Extension Center
$16,062
Brief Project Summary:

Providing recommendations for when fungicide applications are most likely to control Sclerotinia in soybeans has been complicated by the wide range of white mold-associated yield losses. Preliminary data suggests white mold impact on soybean yield is determined by the timing of disease onset and by soybean maturity group, with the highest impact of white mold occurring during the R1-R3 growth stage and when longer-maturity soybean varieties are grown. The project will quantify the impact of Sclerotinia on soybean yield relative to the growth stage at which weather conditions favor white mold as well as maturity rating.

Key Benefactors:
farmers, applicators, agronomists, extension specialists

Information And Results
Final Project Results

Update:

View uploaded report Word file

Executive Report:
A single fungicide application is not always sufficient for protecting soybean yield when risk of white mold is high during soybean bloom, but determining when a second fungicide application is needed can be difficult. This project evaluated the impact of soybean maturity length and white mold infection timing on disease severity and returns to fungicide applications. Replicated field trials were conducted under overhead irrigation in Carrington and Oakes, ND. In Carrington, 38 soybean varieties from 00.5 to 1.0 maturity were evaluated with and without fungicides (zero, one and two fungicide applications targeting white mold); in Oakes, 25 varieties from 0.1 to 1.3 maturity were evaluated. An additional study was established in Carrington in which intensive supplemental irrigation conducive to white mold was delivered during the R2 and R3 growth stages versus the late R3 to early R6 growth stages and compared to a non-irrigated treatment.

Although differences among varieties of similar maturity were observed, susceptibility to white mold was strongly correlated to soybean maturity. In Carrington, end-of-season white mold severity averaged 5% across 00.5- to 00.8-maturity varieties and 39% across 0.9- to 1.0-maturity varieties. In Oakes, end-of-season white mold severity averaged 5% across 0.1- to 0.3-maturity varieties and 16% across 1.1- to 1.3-maturity varieties. In longer maturity soybean varieties, a single fungicide application was often insufficient, and yields were sharply improved by making a second fungicide application.

White mold was most severe when conditions favored disease during the R2 and R3 growth stages (full bloom and initial pod development). Across four soybean varieties from 0.6 to 0.9 maturity, end-of-season white mold severity averaged 31% when intensive irrigation favoring white mold was delivered for a 3-week period during the R2 and R3 growth stages and averaged 13% when intensive irrigation as delivered for a 3-week period from the late R3 to early R6 growth stage. Fungicide applications conferred strong yield gains when conditions were favorable for white mold during R2 and R3 but not when conditions were favorable for white mold from late R3 to early R6.

The results suggest that soybean maturity and growth stage can be used to help guide fungicide decision making. A single fungicide application at R2 may be sufficient for white mold management in most short-maturity varieties (00 through approximately 0.3 or 0.5), and a second application may be needed in many longer-maturity varieties when white mold risk is high during R2 and R3.

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.