Back in the early spring, University of Georgia Extension Plant Pathologist Bob Kemerait predicted that conditions were going to be right for white mold development in peanuts during the 2012 season. He based this on the very warm temperatures common throughout the southeastern United States during the winter of 2011-2012 and spring of 2012. As he noted, white mold develops early and aggressively when soil temperatures are unusually warm early in the season. Unusually warm temperatures did not persist into the planting season, in part because rains cooled the soil. For this reason, early outbreaks of white mold were not as common as Bob predicted; however the disease has come back with a vengeance in the second half of the season. Frequent rain events, lush vine growth, and warm temperatures have created a paradise for white mold in Santa Rosa County. Today, peanut fields throughout our area are exhibiting symptoms of the disease.
Even though a grower may find white mold hits in his field it does not necessarily indicate that a fungicide program has not been effective. No fungicide program will give the grower complete control of soilborne disease in a field. We estimate that, at best, a good soilbourne fungicide program will give 70-80% control under ideal conditions. Growers should expect that an effective fungicide application will prevent that hit of white mold from expanding and traveling down the row infecting adjacent plants.
To monitor your fungicide programs effectiveness, flag the location of a white mold hits in the field and watch the progression (or lack of progress..) of disease in the symptomatic plants.
Late Season Disease Control Considerations
Growers whose crops are approaching harvest have many questions regarding late season disease
control. Below are some basic recommendations for disease management towards the end of the season.
Condition 1. Crop is within two weeks of harvest – there is little opportunity for a fungicide application at this late date to have any benefit for further disease control. Growers will not likely see a benefit from applying a fungicide within two weeks of projected harvest UNLESS the field is threatened by a tropical storm that could significantly delay harvest.
Condition 2. Crop is within approximately three weeks of harvest and disease control (leaf spot and disease) is excellent- grower likely does not need to apply additional fungicide, unless tropical storm threatens extended delay in harvest.
Condition 3. Crop is three or more weeks away from harvest and diseases are still a problem in the field- Grower should consider continuation of leaf spot and, in worst cases, soilborne disease control with fungicides.
Condition 4. Crop is approaching harvest, but not there yet, and diseases are severe in the field. Should the grower dig the peanuts early? If the disease in the field is spotted wilt, the grower is most likely to benefit by allowing the crop to reach harvest maturity before digging. For leaf spot diseases, white mold, and CBR, it is best to let the crop reach harvest maturity IF POSSIBLE, but this is not always possible. Where these diseases are severe in the field, there may be situations where the grower must consider sacrificing some grade for increased yield. Poor control of leaf spot, white mold, and CBR late in the season can result in increasing losses as pegs break and pods are lost at digging.
By: John Doyle Atkins, Santa Rosa County Extension
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