Fungicide-resistant soybean disease found in La.
By Bruce Schultz
PALMETTO, La. – An LSU AgCenter plant pathologist warned farmers at the St. Landry Parish rice and soybean field day on July 25 that fungicide-resistant disease has been found in soybeans in some areas of the state.
The soybean disease aerial blight has developed resistance to fungicides, said LSU AgCenter plant pathologist Clayton Hollier. “That’s very troubling.”
The problem was not unexpected because the rice disease called sheath blight had developed resistance to strobilurin fungicides in the north central area of Acadia Parish in the Mowata community, Hollier said. It has spread to several other nearby parishes.
Sheath blight and aerial blight are basically the same disease, he said.
Hollier cautioned farmers against using low rates of fungicides. He said the practice saves money, but it helps select disease that can survive fungicide applications.
Asian soybean rust has been found in scattered areas throughout the state, but it has not become a problem in commercial fields, Hollier said.
LSU AgCenter rice breeder Steve Linscombe gave an overview of ongoing work at the Rice Research Station to develop new varieties.
Two hybrid lines have done well in tests, but they are too tall for commercial release, Linscombe said, and work on more hybrids is progressing.
“Within a year or two, we’re going to be talking about coming out with a commercial hybrid variety,” he said.
LSU AgCenter entomologist Mike Stout said the stink bug threshold probably will be increased as the result of ongoing research. Currently, the threshold is 30 insects per 100 sweeps for the first two weeks after heading, and 100 insects per 100 sweeps made later than two weeks after heading.
LSU AgCenter rice specialist Johnny Saichuk said stink bugs are a bigger pest than usual. He said a field in northeast Louisiana resulted in 15 stink bugs in just one sweep.
But unlike last year, Saichuk said, he has not found any blast disease.
The biggest problem farmers are having is uneven maturity, Saichuk said. Otherwise, this year’s crop looks good.
LSU AgCenter weed scientist Eric Webster said he is testing a number of new herbicide products for grasses and broadleaf weeds. He said a Gowan product now used in corn is being tested for use in water-seeded rice.
LSU AgCenter soybean specialist Ron Levy said 180 varieties were planted throughout the state at seven locations to get an idea of yield potential. Levy advised growers to select varieties that perform well statewide.
LSU AgCenter agronomist Dustin Harrell said a new product by the Yaravera company combines ammonium sulphate with nitrogen to reduce nitrogen volatilization.
LSU AgCenter plant pathologist Don Groth said rice farmers should continue to scout for disease.
“Once a disease such as sheath blight is in the top of the canopy, there’s nothing you can do,” Groth said. “The damage has already occurred.”
LSU AgCenter entomologist Jeff Davis urged farmers to rotate insecticides to control stink bugs in soybeans. He said overdependence on acephate is resulting in resistance.
With three to five applications needed for soybeans, he said, farmers also should consider using pyrethroids and neonicotinoids.
LSU AgCenter weed scientist Donnie Miller said herbicide-resistant Italian ryegrass problems can be prevented if fields are kept burned down in the fall before the plants have a chance to become established.
LSU AgCenter economist Kurt Guidry said soybeans are expected to stay in the $13-$14 per bushel range, and rice will sell for $24-$27 a barrel.
Randy Jemison of the USA Rice Federation gave an update on the farm bill deliberations.