Each year, test data is poured over by researchers from the University of Georgia, University of Florida and Auburn University in an effort to further fine-tune the Peanut Disease Risk Index. For 2008, the point values for white mold changed in several categories.

“We bumped up the points for white mold with certain varieties,” says Bob Kemerait, University of Georgia Extension plant pathologist, at the recent Georgia Peanut Farm Show. “We also changed the points for white mold on planting date and plants per foot of row.”

The Peanut Disease Risk Index is used in the Peanut Rx™ program, a prescription program that allows growers assess disease risk and, possibly, modify fungicide use as the risk of disease increases or decreases.

The Peanut Rx™ program is based on years of studying the effects of reduced-fungicide spray programs on disease control and pod yields, wherein research has indicated that growers could apply fewer fungicide sprays to some fields without sacrificing disease control or yields.

“In a field where a grower needs less fungicide, he can save money in terms of trips across the field and input costs, yet still make his yields,” says Kemerait.

Austin Hagan, Extension plant pathologist at Auburn University, says, “The benefit of a prescription program is that it improves the efficiency of fungicide use on peanuts so a grower is able to get the most out of his fungicide dollar.”

Hagan advises growers who opt for a reduced-risk program in a reduced-risk field to pay attention to what’s going on in that field in the event a problem does develop, particularly if living near the coast or in an area affected by tropical storms.

“Peanut Rx™ is something good managers are going to be able to use to improve their fungicide efficiency, but like everything else, it will require attention to successfully implement such a program,” Hagan adds.

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Syngenta First To Offer Performance Protection Under Peanut Rx™

With sound scientific data supporting the benefits of a reduced-spray schedule on reduced-risk fields, Syngenta Crop Protection is the first crop protection company to promote prescription fungicide spray schedules for growers at all levels of disease risk.

Working with the co-authors of the Peanut Disease Risk Index – the University of Georgia, the University of Florida and Auburn University – Syngenta agreed to adopt and promote the Peanut Rx™ program, which allows producers to customize a prescription spray program based on the level of disease risk in their field as calculated using the risk index.

“Syngenta believes that smart business decisions are based on smart information,” says Lyle Stewart, Syngenta district manager. “To that end, Syngenta supports Peanut Rx™ because it provides Southeastern growers with the best information available to make those smart disease management decisions.”

Peanut Rx™ is a simple and straightforward method for growers to assess their disease risk level on a field-by-field basis and adopt a prescription fungicide spray schedule to meet disease risk needs, he adds.

Recognizing the impact prescription fungicide spray programs could have on its customers’ bottom lines, Syngenta devised prescription fungicide spray programs for low, moderate and high-risk fields. For fields with low disease risk, fewer fungicide applications may be all a grower needs to produce high-yielding peanuts, whereas a typical five to seven spray program may be necessary for fields with moderate to high disease risk.

“No matter what level of disease risk, Syngenta stands behind its products with its standard product performance protection,” Stewart says. To qualify for Syngenta standard product performance protection under Peanut Rx™, only Syngenta brand fungicides may be used in your spray program.

Minimize Disease Risk

Developing a customized prescription spray program on a per-field basis can be accomplished in four simple steps: assessing your disease risk, calculating your severity points, interpreting your index values and developing your Peanut Rx™. This worksheet can help you through that four-step process of determining your disease risk level in order to customize a Peanut Rx™ for your individual fields.

For each of the risk factors, identify which option best describes the situation in your field and add the index value associated with each choice to obtain your overall disease risk value. This worksheet does not contain all of the varieties included in the 2008 Peanut Rx™ or the notes that accompany each factor. To view the complete 2008 Peanut Rx™ or to assess your disease risk index using the online Web tool, visit the University of Georgia peanut Web site at www.ugapeanuts.com.

Step 1: Assess your disease risk using the categories to the right.

Step 2: Fill in the table on page 13 to calculate your severity points for each of the four major peanut diseases given the 10 determining factors. Total each column to establish your disease index values.

Step 3: Based on your risk values, use the chart to interpret your level of risk for a given field.

Step 4: Once you have calculated your risk total for each fungal disease, utilize the most conservative fungicide program as your guide for customizing a per-field prescription spray program.

A Few Notes About Risk Levels

For spotted wilt, a point total greater than or equal to 115 indicates high risk; 70 to 110 indicates medium risk; and an index total less than or equal to 65 indicates low risk. If a low-level risk is predicted, it is expected that the field would be less likely to suffer major losses due to TSWV than a field rated for a higher level of risk. However, it does not imply that a field is immune from TSWV losses. In a year when TSWV incidence is high statewide, even fields with a low-risk level may experience significant losses.

For leaf spot, a point total of 65 to 100 indicates high risk; 40 to 60 indicates medium risk; and 10 to 35 low risk.

For white mold, a point total of 55 to 80 indicates high risk; 30 to 50 indicates medium risk; 15 to 25 offers low risk. For Rhizoctonia limb rot, a point total of 45 to 75 indicated high risk; 30 to 40 indicates medium risk; 15 to 25 indicates low risk.

It should be noted, when weather conditions are favorable for fungal diseases, especially when rainfall is abundant, even fields at initial “low risk” to fungal diseases may become “high risk.”

If high risk is indicated, growers should use a full fungicide input program.

For medium-risk fields, growers can expect better performance from standard fungicide programs. Reduced-fungicide programs in research studies have been successfully implemented when conditions are not favorable for disease spread.

For low-risk fields, growers have made management decisions, which offer maximum benefit for reducing the potential for severe disease. These fields are strong candidates for modified disease management programs with a reduced number of fungicide applications.

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