Current Risk Report For Peanut White Mold (Stem Rot) Based On Soil Temperatures

 

 

 

 

As soil temperatures are increasing, it is time for peanut growers in Florida, as well as many other areas of the southeast, to consider an early season white mold (a.k.a. stem rot) fungicide spray.  The possibility of low peanut prices in 2016 has led to a need for improved decision making when applying fungicides, which can be done through risk assessment.

 

One of the most important factors to consider in an early season white mold spray decision is the presence of the pathogen (Sclerotium rolfsii) in the field, which can be inferred from cropping history.  However, without the proper environment, the likelihood that disease will develop is severely hindered, making weather data an important component of fungicide spray decisions.  Using soil temperatures collected from various FAWN weather stations (Jay, Marianna, Quincy, Live Oak and Citra, FL), the disease risk levels from 5/9 to 5/11 are no/ low risk in Jay, Quincy, and Marianna, moderate in Citra, and moderate-high in Live Oak (Figure 1).  Last week, risk levels were high in Live Oak and Citra and moderate in Marianna, but the recent cold front brought down these risk levels by ‘cooling off’ soil temperatures across the state. Over the next week or so, we are expecting these risks to remain relatively the same as our current weather forecasts indicate air temperatures will remain relatively cool (< 90°F) for this period.

 

The risk levels shown here are based only on favorable soil temperatures for the fungal pathogen, however adequate soil moisture is also required for fungal growth.  When adding rainfall data to the risk model, disease risk levels drop to low/no risk for all areas reported.  However, irrigation practices should be considered when making management decisions about white mold.

 

 

 

 

The temperature risk model assumes the pathogen is present in your field, and all other environmental and culture conditions are conducive for the disease.  Thus, it is highly recommended that this information be used with the PeanutRx disease risk index to gain a better understanding about the effects of crop rotation, variety, row pattern and seeding rate on the disease.  PeanutRx is available for download as an application on Android and iOS devices.

 

A list of fungicides for white mold control is provided in Table 1 below. More information about PeanutRx and details on available fungicides can be found in the 2016 Peanut Update.