LSU AgCenter plant pathologist Dr. Don Groth hopes the permanent federal label for the fungicide Sercadis is granted for the upcoming growing season.
The chemical’s temporary label expired in August 2013 for use on fungicide-resistant sheath blight.
Groth said the 2013 regulations allowed the use of the fungicide for any areas with the resistant pathogen, but a permanent label would allow the fungicide to be used anywhere rice is grown in the South. The fungicide-resistant pathogen continues to spread and could move into other rice-growing states, he said.
"If it happened here, it can happen somewhere else," Groth said. "We think we have detected it further north into Allen and Evangeline parishes."
The LSU AgCenter scientst said the disease is spread by soil or plant material, adding that the continued use of the same fungicide led to the resistance.
"If you challenge the population enough and put selection pressure against it, a resistant pathogen will develop," Groth explained.
He said the fungicide resistance developed due to a single change in an amino acid of the thousands of combinations in the pathogen’s DNA.
Sercadis at the higher rate in 2013 made the product much more effective, Groth said. The previous rate of 4.5 ounces per acre was increased to 7.6 ounces. Application is most effective normally made around boot stage, he said.
"The consultants I talked with liked it," Groth said. "They thought the rice looked like fields sprayed with Quadris when it first came out."
In addition, the restriction on where the product can be used has been relaxed.
Groth said he is testing several new fungicides that may be available in two to three years. "There’s potential we will have resistance to
Sercadis in five to six years," he said. "If we have another product we could rotate with Sercadis, that would be the ideal situation."
Fungicides have been used on rice since 1977, Groth said. Sheath blight became a problem as more rice farmers started growing soybeans in rotation with rice, and the soybeans also were susceptible to the sheath blight pathogen that causes aerial blight. Before that, most farmers rotated rice with pasture for cattle.
This article was published in the 2014 Louisiana Rice Research Board Annual Report.