A Prescription For More Efficient
Disease Management

Peanut Rx™ helps get the most out of your fungicide dollar.

By Amanda Huber


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.


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.


Crop rotation with non-legume crop
Years Between Peanut Crop Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
0 NA 25 25 20
1 NA 15 20 15
2 NA 10 10 10
3 or more NA 5 5 5
Tillage Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
conventional 15 10 0 0
reduced* 5 0 0 5
Field history
Previous disease problems
in the field?*
Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
NO NA 0 0 0
YES NA 10 15 10
Variety selection
Variety Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
Georgia Green 30 20 25 15
Andru II 25 30 25 25
C-99R 20 15 15 25
Carver 20 30 25 25
AT 3081R 25 30 30 unknown
Georgia-O3L 15 15 10 20
Georgia-02C 15 20 10 20
Georgia-01R 10 10 15 15
York 10 10 10 unknown
AP-3 10 25 10 25
Georgia-05E 15 20 25 unknown
Florida-07 10 20 15 unknown
AT 3085RO 20 30 30 unknown
Does the field receive Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
irrigation?     White mold Limb rot
NO NA 0 0 0
Yes NA 10 5 10
Planting date
Peanuts are planted: Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
Prior to May 1 30 0 10 0
May 1 to May 10 15 0 5 0
May 11 to May 31 5 5 0 0
June 1 to June 10 10 5 0 5
After June 10 20 10 0 5
Row pattern
Peanuts are planted in: Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
Single rows 15 0 5 0
Twin rows 5 0 0 0
Plant population (final stand, not seeding rate)
Peanuts are planted in: Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
Less than 3 plants per foot 25 NA 0 NA
3 to 4 plants per foot 15 NA 0 NA
More than 4 plants per foot 5 NA 5 NA
At-Plant insecticide
Insecticide Used Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
None 15 NA NA NA
Other than Thimet 20G or 15 NA NA NA
Phorate 20G        
Thimet 20G, Phorate 20G 5 NA NA NA
Classic herbicide
Classic Herbicide Usage Spotted Wilt Points Leaf Spot Points Soilborne Disease Points
      White mold Limb rot
Classic Applied 5 NA NA NA
No Classic Applied 0 NA NA NA


A Few Notes About Risk Levels

Calculate Your Risk
  Spotted Wilt Leaf Spot White Mold Rhizoctonia
Crop rotation        
Field history        
Planting date        
Row pattern        
Plant population        
At-plant insecticide        
Classic herbicide        

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.

Interpret Your Index Values
  Spotted Wilt Leaf Spot White Mold Limb Rot
Low Risk < 65 10-35 10-25 15-25
Moderate Risk 70 -110 40-60 30-50 30-40
High Risk >115 65-100 55-80 45-75

In a year when tomato spotted wilt virus incidence is high statewide or in your region, even fields with low risk level may experience significant losses. Consider the following recommendations to reduce your spotted wilt risk level:

• Use less susceptible varieties.
• Adjust planting date.
• Consult the complete Peanut Rx™ for additional options that may also provide limited benefit.

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.