White Mold - Risk Assessment

These mushroom-like structures on the soil surface are the beginning of the white mold disease cycle and are favored by dense canopy growth.

The growth and activity of the white mold fungus are governed by the environment in the crop canopy, and is particularly favored by dense soybean canopies.

Rain events during flowering, and areas of fields where moisture collects due to fogs and extended dew periods are especially favorable for fungal growth. Risk assessment for white mold is based on these factors, as well as the field history, soybean variety and other factors. The presence or absence of significant risk factors can impact the benefits of management tactics.

Seasonal risk factors	Long-term risk factors
Weather Moderate temperatures (<85 F), normal or above normal precipitation, soil moisture at field capacity or above. Prolonged morning fog and leaf wetness (high canopy humidity) at flowering into early pod development. White mold potential is reduced if air temperatures of 90 F or above occur during flowering and early pod development.	Field/cropping history Pathogen population will gradually increase if other host crops are grown in rotation with soybean only 1- to 2-year intervals occur between soybean crops white mold susceptible varieties are grown. Including a small grain in the rotation lowers risk of white mold.
Early canopy closure Early closure due to early planting, high plant population, narrow rows, and excessive plant nutrition, together with optimal climatic conditions creates a dense canopy and increased numbers of apothecia on the soil.	Weed management systems Inoculum will increase if control of broadleaf weeds is ineffective. Some herbicides used in rotation systems may be suppressive to white mold
History of white mold It's difficult to eradicate the pathogen from infested fields. The apothecia are responsive to weather and crop canopy, and are present on soil surface at the flowering. The distribution of pathogen/disease in field is usually not uniform but occurs in "hot spots".	Topography of field Pockets of poor air drainage, tree lines and other natural barriers to impede air movement will create favorable microenvironment for white mold development.
Soybean variety planted Plant structure and physiological functions govern variety reaction to white mold. Varieties range from partially resistant to highly susceptible. Variety reactions are variable if management practices and weather conditions promote excessively dense crop canopies.	Pathogen introduction (1) contaminated and infected seed (2) movement of infested soil with equipment (3) wind-borne spores from apothecia from area outside fields.

Plant Health Initiative

White Mold - Risk Assessment