Farmers get relief from rice diseases in 2014

Frances Gould, Schultz, Bruce  |  3/4/2015 3:37:30 AM

Don Groth, LSU AgCenter pathologist, at right, talks with crop consultant Doug Leonards about disease symptoms during a field day at the Rice Research Station.

Disease in rice was not as big of a problem in 2014 for most growers as in previous years, according to LSU AgCenter plant pathologist Don Groth.

“With as much rain as we had, sheath blight wasn’t as bad as it could have been,” he said.

The cold winter of 2013-14 could have played a role in the low incidence of disease, Groth said, but the mild disease year can also be attributed to the direct result of breeding efforts that have been selected for disease resistance.

That selection took place through several years. “We have a lot fewer very susceptible and susceptible lines in our nurseries, and resistance is being increased in the breeding process,” he said.

Current high yields would not be possible without disease resistance, he said.

Bacterial panicle blight wasn’t bad in 2014, Groth said, because temperatures were moderate, and blast was not found until late in the growing season. Blast resistance in variety development was increased with the bad outbreak of the disease in 2012, and that eliminated many blast-susceptible lines.

Out of the almost 800 advanced lines he evaluated for the disease in 2014, Groth said, only four or five showed signs of severe blast.

Many of the lines susceptible to Cercospora have also been eliminated. Groth suspects many farmers are spraying for that disease, even though it may be unnecessary.

It’s likely that fungicide-resistant sheath blight is continuing its spread in south Louisiana, he said. “But we have the tools to manage it.”

The main line of defense, Sercadis, should be applied at 6.8 ounces an acre because the lower rate of 4.5 ounces does not last long enough, Groth said. Convoy fungicide also had good activity against both the wild and resistant sheath blight fungi.

Groth tested six new fungicides in 2014, and he expects that two could be available by 2015 or 2016. “Some of them look really good,” he said.
 
But the new fungicides only have activity against sheath blight. “We really don’t have any new products for blast, and that has me worried,” he said.

A generic version of Quadris Equation will be available in 2015 because the patent on azoxystrobin, the active ingredient, has expired.

Groth will start a study in 2015 to look at the benefit of fungicide use on currently available, moderately susceptible varieties compared with not spraying any of the products.

“There is a question if earlyplanted moderately-susceptible rice varieties need to be sprayed,” Groth said. “Somewhere along the line, we need to cut costs in rice production, and fungicide use is one possible area.”

This article was published in the 2015 Louisiana Rice Research Broad Annual Report

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