Last updated by
Nick Dolezal
on February 20, 2002

Common Names of White Mold:

    None Found

Causal Agent:

Species:
    Sclerotinia sclerotiorum (de Bary)

Class:
    Fungi

Order:
   Ascomycetes

Host Range:

Here are some of the alternate crops, ornamentals, and weeds that White Mold can survive on.  One site listed over 300 plant species that can be hosts for white mold!
 

Geographical Range:

    Sclerotinia sclerotiorum was first discovered in Illinois in 1948 and has since spread throughout the central and northern plains.  White mold problems have increased, in the recent years, due to added usage of the soybean in farm crop rotations.  Also, the incorporation of narrower rows has lead the disease to thrive as will be explained later.

Symptoms:

    White mold can be detrimental to a soybean crop as displayed in the picture on the home page.  A farmer or scout may first notice this problem when gray lesions appear near or on the base of soybean plant stems.  If the disease has progressed a bit further in it's life cycle, then white mycelium may be present near the same areas as the lesions on the plant.  Sclerotia, which are dark structures that look like mouse droppings, appear in the inside of stems and pods as well as the along outside.  Stems and pods will eventually die and leave the brown plants covered in mycelial growth sticking straight up in a bean field. 

Dissemination:

     White mold can be moved from field to field by the transfer of infected seed, manure, equipment, and soil.  The ability of the disease to spread is the reason it has become such a problem in recent years.  Infected soybean stems and seeds may be transported with combines or tillage equipment, leaving primary inoculum in the field for the next growing season.  The sclerotial particles are similar in size and shape to soybeans, so a harvester cannot separate the structures from soybean seeds very easily, as displayed in the photo at of this page.

Disease Cycle: 

     The disease cycle begins in the spring with primary inoculum in a field.  Mycelium or sclerotia present in the soil, soybean seed, or plant debris germinates and produces structures called apothecia.  These apothecia produce asci and ascospores which are dispersed by the wind.  The spores then come in contact with a host plant, like a soybean, and germinate.  After some growth and development, as a result of  the robbing of nutrition from the plant, mycelium rots the plant and sclerotia is formed.  The plant eventually dies and the mycelium and sclerotia are left to over winter for the next year's primary inoculum. 

for an illustration of the white mold disease cycle click here!
 

Control Measures:
     The easiest way to control white mold infection is to control the transfer of primary inoculum, mycelium and sclerotia.  This can be accomplished most easily by thoroughly cleaning equipment between fields and making sure clean seed is used for planting.  Also, white mold flourishes in fields which are cooler and more moist.  To prevent the perfect environment for white mold a good drainage system should be in place throughout a field.  Planting in wider rows will prevent crop canopy and allow for increased light penetration and wind currents below the canopy making for a drier, more unfavorable environment for white mold.

Recent Research Summary:

Related Journal Article:

Reglinski, T. Whitaker, G. Cooney, J. Taylor, J. Poole, P. and Roberts, P.  Mar, 2001.  Systemic acquired resistance to Sclerotinia sclerotiorum in kiwifruit vines. 
     Physiol-mol-plant-pathol.  58:111-118.

    The reason for the study performed here was to find out if an application of salicylic acid to kiwifruit vines reduced the infection of Sclerotinia throughout the plant.  Fruit vines were injected with 0.2mM salicylic acid in various places adjacent to a white mold lesion.  As a result, a 25-35% reduction in lesion appearance in adjacent leaves in the direction of the trunk was realized.  However, no effect was realized on leaves in the direction of the shoot tip. This study may lead to the possibility for treatment for white mold in the future.

Sources:

Agrios, George N. 1997.  Plant Pathology 4 ed.  Academic Press.
        pp. 354-358.

Common Names of Plant Diseases
     http://www.apsnet.org/online/common/query.asp

NCSRP Web site.
        http://www.ncsrp.com/whitemold/factsheet.htm

University of Illinois.  Extension Web site.
     http://www.whitemold.uiuc.edu/

University of Minnesota. Extension Web site.
        http://www.soybeans.umn.edu/crop/diseases/sudden_death.htm
 

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