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Blast hits Louisiana ryegrass

BATON ROUGE, La. — LSU AgCenter scientists are keeping a watchful eye on a fungal disease known as "blast" that is taking a toll on this year's ryegrass crop.

According to LSU AgCenter forage specialist Ed Twidwell, the disease was seen on a widespread basis this fall in both Louisiana and Mississippi. "The most probable cause of blast this fall is the warm, wet and humid conditions in mid- to late October," Twidwell said.

The disease is especially hard on cattle producers who didn't have good luck with hay this year, Twidwell said.

"The blast will reduce the time that producers have for winter grazing, but the ryegrass can be reseeded," Twidwell said, explaining symptoms of blast are round to oval lesions with gray centers on the grass blades.

LSU AgCenter forage researcher Brad Venuto, who is located at the AgCenter's Southeast Research Station in Washington Parish, said this disease is hitting beef and dairy producers extremely hard — because they depend on the ryegrass to help them sustain their herds through the winter.

"It's really tough on the dairy producers here in the Southeast region because they were already up against some really depressed milk prices and now the extra expense that this will cause is going to be tough," Venuto said.

Infection with this disease occurs when plants are exposed to 24 hours or more of continued leaf wetness, according to experts, who say that if a large number of plants in a given field become infected, the field will take on a gray appearance.

LSU AgCenter county agent Kenny Sharpe of Livingston Parish said the fungus has been found in that parish, as well as other areas.

"We've been checking different areas of the parish and where it's found it looks like the grass has exploded," Sharpe said of ryegrass affected by the fungus.

LSU AgCenter scientists say the disease has the potential to kill or severely damage young ryegrass seedlings and that producers may have to reseed some areas of their pastures.

Twidwell said ryegrass that has 3 to 6 inches of growth is okay for light grazing even if it has blast. In fact, the specialist said such grazing would remove older dead leaves and allow some sunlight to penetrate the ryegrass canopy.

On the other hand, Twidwell said no fungicides are labeled for the control of blast on ryegrass, so the best possible cure for the disease will be plenty of dry, cool weather and sunshine.

For additional information on the blast problem in ryegrass, contact a county agent in your parish LSU AgCenter Extension office.

Johnny Morgan writes for the LSU AgCenter.

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