Dean Malvick, Extension plant pathologist, Angie Peltier, Regional Educator - Crops, & Anthony Hanson, Regional Educator - Integrated Pest Management
Nearly every year white mold develops to damaging levels in some Minnesota soybean fields. That includes last year in areas that received timely rains in July and early August when it was very dry in most other areas throughout July and August
White mold is favored when soybean plants are flowering, the rows are closing, soil is moist for 10+ days and both stems and leaves are wet and temperatures below 68°F for prolonged periods of time (Fig. 2). But we also see outbreaks of white mold when all of these conditions don't seem to have to been met.
In much of Minnesota recently, the day and night temperatures were too warm to favor white mold. However, with the recent rains in some areas and cooler temperatures in the forecast, white mold could now or soon be developing in soybean fields. As of July 3, 2023, 29% of Minnesota soybeans were blooming based on the USDA-NASS Crop Progress and Conditions report, with much higher percentages occurring in some areas.
White mold risk can be reduced in advance with partially resistant soybean varieties, reduced plant populations, and wide rows. At this time of the season, fungicides are one of the few options available that can reduce white mold severity where the disease risk appears to be high. Unfortunately, white mold can persist in the soil for years and will not be removed entirely from a field through rotation in later years.
Source: umn.edu
Photo Credit: istock-ds70
Categories: Minnesota, Crops, Soybeans