Researchers monitor plots for Asian soybean rust

Johnny Morgan, Bollich, Patricia A., Hollier, Clayton A.  |  5/29/2013 12:27:33 AM

News Release Distributed 05/28/13

BATON ROUGE, La. – LSU AgCenter personnel are looking for Asian soybean rust in kudzu and soybean sentinel plots across the state.

Since 2005, LSU AgCenter scientists have been searching for the disease by planting soybean sentinel plots two weeks before farmers plant their soybean crops to observe whether the rust is in the area, said LSU AgCenter plant pathologist Clayton Hollier.

“My associate, Patricia Bollich, has been scouting on a part-time basis since the very beginning of the year,” Hollier said. “And she has found rust on kudzu leaves that survived from last year.”

The difference this year is the fungus has been found earlier than in the past, Hollier said.

Another first is finding rust on young, volunteer soybean plants that grew from seed spilled last year.

“I don’t want to alarm people, but this is the most advanced situation that we’ve seen this time of year with rust,” he said.

Observers are looking for rust on kudzu earlier in the season because it’s an indicator of how well the fungus survived the winter.

“It overwinters in kudzu all the time,” Hollier said. “But we have indications that we have more soybean rust overwintering here than we’ve ever had.”

This happens in Florida regularly, but experts believe the mild winter is responsible for the earlier detection in Louisiana this year, he said.

Hollier said with closer examinations with a microscope “you find that these are not old pustules that survived on old leaves but are new ones that are producing new spores.

“This is new and different from what we’ve had in the past,” he said. “This sends up a red flag.”

Early detection made Hollier more interested in the coastal parishes where the fungus could survive in kudzu that was not frozen.

“So we looked in other locations and found it in a dozen sites in eight of the coastal parishes and as far north as East Baton Rouge,” he said.

Other parishes where the disease was detected included Terrebonne, Lafourche, Iberia, Lafayette, St. Mary, St. John and Vermilion.

Bollich looks at 25 to 30 kudzu sites and 15 or so soybean sentinel plots each year, Hollier said.

Early-planted sentinel plots provide an indicator for commercial growers that the disease is present.

“The idea is to plant the sentinel plots two to three weeks before the commercial crop, so we can tell if we have rust ahead of the growth stage of the commercial growers,” Hollier said.

Observers have not found the rust on new soybeans this year, but Hollier said a lot of acreage is yet to be planted.

The disease is known to attack more than 100 host plants, with soybeans and kudzu the most susceptible.

Soybean growers are advised to be vigilant, but they shouldn’t panic. Hollier said this year’s development of the disease would be historic for its early start, but actually it means that growers may have to act earlier to control the fungus.

Asian soybean rust was first found Louisiana in 2004 and is believed to have been brought by winds from Hurricane Ivan early that fall.

Even if the disease gets an early start this year, growers have several chemicals that are very effective, Hollier said.

Scientists and growers initially were alarmed by the first sighting of the disease in 2004, when LSU AgCenter scientist Ray Schneider found the disease in a field on the Ben Hur Research Farm near the LSU campus. This was the first discovery of the disease in North America.

Asian soybean rust has been known to exist since 1902 when it was found in Japan. It was largely confined to Asia until recently – when it spread to Africa and then on to South America around 2000.

“In some of these countries, the disease actually caused 100 percent crop failure,” Hollier said.

Johnny Morgan
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