A new product and earlier expression of the disease warrant earlier control measures.
By Amanda Huber
White mold has been the primary disease problem in peanuts for the last four years in a row. Because of its widespread distribution, sheer number of hosts and potential for the sclerotia, or survival structures, to survive in the soil for a number of years, it is no wonder this disease poses the greatest threat year after year.
Not ‘If’ But ‘When’
“If you grow peanuts, you have white mold. If you grow soybeans, you have white mold. White mold can affect cotton to some degree. It can grow in vegetables,” says Bob Kemerait, University of Georgia Extension plant pathologist.
“We will always have conditions sometime during the year that are favorable for white mold outbreaks,” he says. “It’s not ‘if’ you are going to have white mold, but ‘when’ you are going to have it.”
The hotter it becomes earlier in the season, the more likely it will be that white mold expresses itself earlier.
“Temperature drives white mold,” Kemerait says.
An Early Emergence Application
The earlier expression of white mold, based on favorable conditions, means that producers need to consider starting their fungicide programs earlier, and a new product, Proline, is being recommended for an early emergence application.
“What causes us to rethink the impact of white mold is that it does not start at 60 days after planting in a year like 2010 or 2011; it starts two, three or four weeks after the plants come up,” Kemerait says. “Proline applied at early emergence, two to five weeks after planting, is something to consider.”
Use Peanut Rx to assess the risk for white mold based on specific production strategies and how to reduce risk by manipulating those strategies. One of the most important strategies in pest control is always rotation.
“Rotate away from the most susceptible crops, and to reduce the buildup of inoculum in the top few inches of soil, deep turn the soil to bury those fungal spores out of reach of the crop,” Kemerait says.
Currently, the variety Ga-07W has some resistance to white mold, but peanut breeders are working to screen for more resistance.
Plan An Appropriate Program
A fungicide program is a needed component to managing white mold. “Fungicides are an added cost, but it is an outstanding investment,” Kemerait says.
It is recommended to time fungicide applications to correspond with the growth of the crop, the threat from white mold, based upon soil temperature and rainfall/irrigation, and the anticipation of rain events or irrigation to help move the fungicide from the foliage to the crown of the plant.
“If you know that white mold conditions favor expression of the disease earlier, start your fungicide program earlier,” Kemerait says.
Also recognize that more recently released products offer more control than products released more than a decade ago.
Finally, spraying at night or in the early morning hours before dawn has been proven to allow for more effective control because of the fungicides ability to get at the target area of the plant without as much interference from the leaves.
White mold management strategies continue to evolve with new products, new varieties and new application methods. PG
New Recommendation: Proline Early Emergence
Research efforts at the University of Georgia in 2010 and 2011 have documented that applications of Proline at 5.7 fluid ounces per acre or the “broadcast rate” applied banded over young plants two to five weeks after planting can have a significant and season-long benefit for managing white mold.
The active ingredient in Proline 480SC is prothioconazole. Prothioconazole and tebuconazole are the active ingredients in Provost fungicide. Applied in-furrow at planting, Proline aides in the management of Cylindrocladium black rot. However, when applied to the peanut crop after emergence, Proline can provide season-long benefits to the management of white mold and possibly Rhizoctonia limb rot as well.
As a new recommendation, growers should carefully consider the following:
• An early season application of Proline is unlikely to provide all of the needed control. Follow an early season application of Proline with a standard soilborne fungicide program.
• Apply the full rate of Proline banded over the young peanuts planted in either single rows or in twin rows at 20 to 40 gallons per acre. If planted in twin rows, the fungicide can be applied with either a single-nozzle covering both twins at once at 20 to 40 gallons per acre or with a single nozzle over each of the twin rows at 10 to 20 gallons per acre per nozzle. Growers should use an even “flat-fan tip” for this application.
For additional information on the use of Proline in an early emergence application, read the University of Georgia’s 2012 Peanut Production Update available on their Web site at www.caes.uga.edu/commodities/fieldcrops/peanuts. Click on “2012 Peanut Production Update Guide” under the Quick Links tab in the lower right of the page. PG