Sorghum Ergot Jumps Border into New Mexico
Date: Oct. 20, 1997
Editor: D'Lyn Ford (505) 646-6528, dlford@nmsu.edu
LAS CRUCES - Sorghum ergot, a yield-reducing grain disease, crossed from Texas into eastern New Mexico, where it infected a field of seed sorghum on private land near Clovis earlier this month.
"Sorghum ergot has been spreading through Texas, and we've been waiting for it to get to New Mexico," said Natalie Goldberg, plant pathologist with New Mexico State University's Cooperative Extension Service. "Fortunately, because it didn't arrive until late in the year, damage this season was almost nonexistent."
NMSU researchers confirmed the disease Oct. 7 in a field of hybrid sorghum-sudan grown for breeder seed near Pleasant Hill, about a mile from the Texas border. Scientists had planted trap crops of susceptible sorghum at NMSU's agricultural science centers at Artesia and Clovis, but they were harvested and plowed down several weeks ago.
"The disease needs night temperatures around 55 degrees, and we may have plowed or chopped it up before we got those temperatures for infection," Goldberg said.
Farmers had been expecting the fungal disease, which infests sorghum heads and leaves them dripping with honeydew. Some growers had treated sorghum with a preventive fungicide approved especially to combat the disease.
Before this year, sorghum ergot had never been detected in the United States. The disease initially turned up in South Texas' Rio Grande Valley and was recently found in the Texas Panhandle adjacent to eastern New Mexico.
Sorghum ergot greatly reduces yields, though the disease does not make grain toxic. In wheat and rye, ergotism makes grain poisonous. Sorghum ergot also lowers grain and seed quality.
"This disease is going to be a serious problem for seed producers because it infects the unfertilized ovary and prevents the seed from forming, so you have a loss of yield," Goldberg explained. "In the area where it was found, they do a lot of seed production, so the large growers will have to prepare for it every year."
The sticky honeydew from sorghum ergot gums up harvesting equipment, Goldberg added. Early in the season, the disease can reduce germination and seedling emergence and predispose seedlings to other diseases.
Because the sorghum ergot fungus multiplies and spreads readily via farm equipment, clothing, wind and insects, it is likely to stay in New Mexico, Goldberg said.
"The only problem with the fungicide we received a special permit for this year is that you can get phototoxicity, meaning that if it's used repeatedly or improperly it can injure the plants," Goldberg said. "I think in the long run we're going to be looking towards resistant varieties as our best avenue toward management, and I think there is some indication from breeders that it will be a possibility." Other fungicides could also prove effective with a lower risk of injuring crops.
Cultural practices, such as adjusting planting dates to avoid the lower night temperatures the fungus prefers, are another weapon, Goldberg said. Removing side tillers also could help, though it could be too difficult or costly.
New Mexico typically has 165,000 to 175,000 acres of sorghum, most of which is harvested for grain, said Darrell Baker, acting superintendent for NMSU's Agricultural Science Center at Clovis. Sorghum use for forage has risen to about 30,000 acres because of dairy growth, he said.