| Disease: White Mold |
 |
 |
 |
 |
 |
 |
| Soybean varieties differ in their response to white mold infection. |
White Mold - Resistant Varieties
Soybean variety selection is the foundation of a management plan to minimize yield loss to white mold. Varieties can be characterized for their reaction to white mold and can be used to maximize yield in the presence of white mold, as well as to minimize the survival and activity of the white mold pathogen.
One or a combination of traits appears to be involved in how a soybean variety reacts to the white mold pathogen. These inherent physiological traits determine the rate and severity of symptom development, plant architecture, lodging traits, maturity group, and response to management practices that govern canopy development. Early maturity varieties will sometimes express less white mold, but this trait cannot be relied upon each year.
How varieties are evaluated
The reaction of soybean varieties to the white mold pathogen is expressed as a percentage of the plant population which express symptoms, and the severity of symptoms within the population of symptomatic (diseased) plants. Long-term field trials indicate that for each 1% increment of plant mortality at the R6-7 growth stages, soybean yield is reduced 0.25 to 0.50 bushels per acre. For example, a variety that expresses 20% plant mortality is losing 5-10 bushels per acre of yield potential to white mold.
Five “reaction types” are used to describe soybean variety performance in the presence of white mold and serve as guidelines for selecting soybean varieties for fields with high white mold potential.
We recommend that yield in the presence of white mold be used as the primary criterion in selecting varieties for fields with a history of white mold. When reviewing test data, consider a variety relatively susceptible if it expresses greater than 25% plant mortality.
Table 1. Reaction types of soybean varieties in the presence of white mold.
Reaction Type |
Plant mortality and yield |
Comments |
| Resistant | Plant mortality <5% | Currently not available |
| Partially resistant | Plant mortality 5-25% | Currently the highest form of resistance available. Low reproduction of white mold fungus associated with this variety type. May aid in eventually reducing sclerotia density in soil. Can be used in conjunction with management practices designed to maximize yield. |
| Moderately susceptible | Plant mortality: 26-50%
Plant mortality and yield is variable by year and location, but can be comparable to partially resistant varieties especially when white mold pressure is moderate. Moderately susceptible varieties are clearly inferior in high white mold environments. |
Varieties of this reaction type may be needed if other traits are needed, but not found in partially resistant varieties. Varieties of this reaction type can be considered for fields/management systems that are of moderate to low risk for white mold. Yield is acceptable but varieties of this reaction type may increase inoculum and increase risk of white mold in consequent years. |
| Susceptible | Plant mortality: 26-50% Yield is seldom acceptable in the presence of white mold. Many varieties within this group express inconsistent reactions from trial to trial. Variable performance related to the ability to escape white mold. |
High risk reaction type in high white mold potential environments. A lower risk if used in conjunction with practices designed to reduce crop canopy density, but will fail in years with high white mold potential.
|
| Highly susceptible | Plant mortality: >50% Very low yield in the presence of white mold. |
This type of variety should be avoided in fields with even a low risk of white mold. Varieties within this group are consistently the poorest performing varieties in white mold trials. |
Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.