Rice Farming

Today’s crop consultants no longer simply make recommendations; they write prescriptions.

“There are hundreds of different environments, and what works on one field may not work on another,” says Dr. Rick Cartwright, University of Arkansas Extension plant pathologist in Little Rock. “The fungicides we have today are more or less prescriptive products. For every disease, there is an effective product, rate and timing, and all of those things need to be used together to get the most bang for your buck. It’s become almost like human medicine, where you diagnose the problem, then prescribe a treatment.”

The question, of course, is which prescription works best under which conditions? The answer has become more complex with the introduction of several new fungicide options, such as Gem and Stratego from Bayer CropScience. The active ingredient in Gem is trifloxystrobin, a strobilurin fungicide. Stratego combines trifloxystrobin and propiconazole, the active ingredient in Tilt. Gem is strong against blast, while Stratego is effective against sheath blight as well as several secondary diseases.

Several factors should be considered before selecting a fungicide:

• Target disease: “Each disease has its own cycle, and control practices are effective only at certain stages when the pathogen is susceptible to the chemical control and before irrevocable damage occurs,” says Dr. Donald Groth, a plant pathology professor at Louisiana State University’s Rice Research Station.

• Multiple diseases: The decision becomes more complex if more than one disease is present.

“Fungicides should be applied to control diseases to which the variety is most susceptible,” says Dr. Allen Wrather, a professor at the University of Missouri’s Delta Center. “Use the most effective fungicide for sheath blight control if sheath blight is the only disease present. However, if blast is present or anticipated, use the most effective fungicide for blast control in the second application.”

• Treat for the disease that is the greatest threat to profits, adds Johnny Saichuk, Extension rice specialist at the LSU AgCenter.

“If more than one is present, determine the one most likely to cause a yield or quality reduction,” he says. “Then select the fungicide both labeled and recommended by the state Extension and research personnel.”

• Variety selection: Resistant varieties are not foolproof, and farmers often opt for increased yield potential over genetic resistance.

“Disease resistance is the best control method, but it often it is not available or breaks down after varietal release,” Groth says. “Most long-grain varieties are susceptible to sheath blight, and several major varieties are susceptible to blast.”

• Field history: “To select the right fungicide, farmers should know the history of disease in his field or at least his geographic area, know the reaction of the variety being grown to the prevalent diseases and identify the diseases correctly,” Saichuk says.

• Agronomic practices: Farming practices can affect the severity of certain diseases.

“Watch the use of nitrogen fertilizer,” Cartwright says. “Once you reach recommended rate, the only thing you are feeding is disease.”

• Length of control: The objective is to apply a fungicide that will protect the crop through harvest. Efficacious new fungicides make that goal more attainable.

“With the new fungicides, we are very capable of stopping sheath blight in its tracks,” Cartwright says. “We need to understand how long each product will last. For example, a fungicide at full rate may suppress a disease for 28 days, which may be long enough for a short-season variety. But you may be able to wait until boot stage, apply a three-quarters rate and get 21 days of suppression.”

• Economics: “If two or more fungicides are recommended,” Saichuk says, “then select the most economical treatment.”

At a time of rising input costs and stagnant market prices, economics take on added importance. That makes some of the newer fungicides appealing.

“Stratego is priced very competitively,” Cartwright says, “which got the attention of a lot of farmers who found they could use a premix for less money.”

Perhaps the most important criterion is selecting a fungicide that will help farmers reach their yield and quality objectives. That requires putting a pencil to the paper to determine the potential return on investment.

“Varieties such as Wells and Francis have the capability to make 200-plus bushels,” says Dr. Ronnie Helms, a farmer and consultant in Stuttgart, Ark. “You would be more likely to use fungicides on them than on a crop where you expect to make 130 bushels.

“You don’t run a 100-yard race and quit at 95 yards.”

For questions or comments, contact Rice Farming editor Vicky Boyd at (209) 571-0414 or vlboyd@att.net.

Prescription for success: Follow these integrated steps to get the most from your fungicide
By Alan Goforth
Today’s crop consultants no longer simply make recommendations; they write prescriptions. “There are hundreds of different environments, and what works on one field may not work on another,” says Dr. Rick Cartwright, University of Arkansas Extension plant pathologist in Little Rock. “The fungicides we have today are more or less prescriptive products. For every disease, there is an effective product, rate and timing, and all of those things need to be used together to get the most bang for your buck. It’s become almost like human medicine, where you diagnose the problem, then prescribe a treatment.” The question, of course, is which prescription works best under which conditions? The answer has become more complex with the introduction of several new fungicide options, such as Gem and Stratego from Bayer CropScience. The active ingredient in Gem is trifloxystrobin, a strobilurin fungicide. Stratego combines trifloxystrobin and propiconazole, the active ingredient in Tilt. Gem is strong against blast, while Stratego is effective against sheath blight as well as several secondary diseases. Several factors should be considered before selecting a fungicide: • Target disease: “Each disease has its own cycle, and control practices are effective only at certain stages when the pathogen is susceptible to the chemical control and before irrevocable damage occurs,” says Dr. Donald Groth, a plant pathology professor at Louisiana State University’s Rice Research Station. • Multiple diseases: The decision becomes more complex if more than one disease is present. “Fungicides should be applied to control diseases to which the variety is most susceptible,” says Dr. Allen Wrather, a professor at the University of Missouri’s Delta Center. “Use the most effective fungicide for sheath blight control if sheath blight is the only disease present. However, if blast is present or anticipated, use the most effective fungicide for blast control in the second application.” • Treat for the disease that is the greatest threat to profits, adds Johnny Saichuk, Extension rice specialist at the LSU AgCenter. “If more than one is present, determine the one most likely to cause a yield or quality reduction,” he says. “Then select the fungicide both labeled and recommended by the state Extension and research personnel.” • Variety selection: Resistant varieties are not foolproof, and farmers often opt for increased yield potential over genetic resistance. “Disease resistance is the best control method, but it often it is not available or breaks down after varietal release,” Groth says. “Most long-grain varieties are susceptible to sheath blight, and several major varieties are susceptible to blast.” • Field history: “To select the right fungicide, farmers should know the history of disease in his field or at least his geographic area, know the reaction of the variety being grown to the prevalent diseases and identify the diseases correctly,” Saichuk says. • Agronomic practices: Farming practices can affect the severity of certain diseases. “Watch the use of nitrogen fertilizer,” Cartwright says. “Once you reach recommended rate, the only thing you are feeding is disease.” • Length of control: The objective is to apply a fungicide that will protect the crop through harvest. Efficacious new fungicides make that goal more attainable. “With the new fungicides, we are very capable of stopping sheath blight in its tracks,” Cartwright says. “We need to understand how long each product will last. For example, a fungicide at full rate may suppress a disease for 28 days, which may be long enough for a short-season variety. But you may be able to wait until boot stage, apply a three-quarters rate and get 21 days of suppression.” • Economics: “If two or more fungicides are recommended,” Saichuk says, “then select the most economical treatment.” At a time of rising input costs and stagnant market prices, economics take on added importance. That makes some of the newer fungicides appealing. “Stratego is priced very competitively,” Cartwright says, “which got the attention of a lot of farmers who found they could use a premix for less money.” Perhaps the most important criterion is selecting a fungicide that will help farmers reach their yield and quality objectives. That requires putting a pencil to the paper to determine the potential return on investment. “Varieties such as Wells and Francis have the capability to make 200-plus bushels,” says Dr. Ronnie Helms, a farmer and consultant in Stuttgart, Ark. “You would be more likely to use fungicides on them than on a crop where you expect to make 130 bushels. “You don’t run a 100-yard race and quit at 95 yards.” For questions or comments, contact Rice Farming editor Vicky Boyd at (209) 571-0414 or vlboyd@att.net.
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