Importance:
Soybean farmers in Minnesota continue their valiant battle to protect yield potential
from the fungus that causes white mold. Disease is favored by cool to moderate
maximum daily temperatures and moisture from rain, fog, dew or high relative
humidity and a dense canopy during the beginning flowering through beginning pod
growth stages. Many of the production practices that have been adopted to maximize
yield potential also favor white mold. Annual yield losses in Minnesota soybean due
to white mold have been estimated to be as high as $120.3 million. Even when one
adopts all of the recommended integrated white mold management strategies, yield
loss occurs in years that favor disease. A radical improvement in canopy penetration
and coverage of fungicides has the potential to be a game changer when it comes to
in-season white mold management. The proposed project aims to do just that.
Objective: A New Approach to Managing White Mold in MN Soybean.
The problem. White mold is an economically important disease caused by a soilborne fungus called Sclerotinia sclerotiorum. The pathogen has a very wide host
range including soybean, dry edible bean, sunflower, canola, sugar beet, peas and
snapbeans (Boland and Hall 1994), crops of economic importance to Minnesota. In
soybean, spores land on and colonize senescing soybean flowers that remain
attached to the plant at leaf axils. The fungus uses this food source to infect the stem.
Disease is favored by cool to moderate maximum daily temperatures and moisture
from rain, fog, dew or high relative humidity and a dense canopy during the beginning
flowering through beginning pod growth stages. Many of the production practices that
have been adopted to maximize yield potential such as early planting, narrow row
widths, high plant populations and high soil fertility tend to favor a dense canopy and
therefore also favor white mold (Peltier et al. 2013). From 1996 through 2017 annual
yield losses in Minnesota soybean due to white mold were estimated to be as high as
3.2 percent, with up to 13.3 million bushels lost (Table 1). Disease losses were as
high as $14.8 per acre and $120.2 million total (Table 1).
Table 1. Annual Minnesota soybean acreage, production and value and percent t