June 23, 2005
Source: StopSoybeanRust.com, 22 June 25 [edited]
<http://www.stopsoybeanrust.com/viewStory.asp?StoryID=389>

Rust-like spores found in Louisiana State University AgCenter's spore trap near St Joseph, Louisiana

Spores similar to those associated with Asian soybean rust [ASR] have been found in a trap set up by the Louisiana State University AgCenter in a soybean field near St Joseph, LA, which is in the north east part of the
state near the Mississippi River.

According to David J Boethel, vice-chancellor for research at the LSU AgCenter, there is no cause for alarm. The small number of spores precludes confirmation at this time. But they appear similar to those that cause ASR,
and scouting efforts should be increased.

Word about the resemblance of the spores to the kind that cause ASR came late on Tuesday (21 Jun) from a laboratory at the University of Arkansas. As of 7:45 pm CDT, no notice of the find has been posted on <http://www.sbrusa.net> either as a state commentary or in the national Soybean Rust Forecast.

Ray Schneider, the LSU AgCenter plant pathologist, who discovered ASR for the 1st time in North America in a soybean field near Baton Rouge, said the Arkansas lab was recently established to run tests of spores from spore
traps sent in from soybean-producing states. Funding for the trapping system is being provided by Syngenta, Schneider said. The traps, on stakes in selected soybean fields across the state, include a slide (for a microscope) covered with a sticky substance, Schneider said. These slides are sent to the Arkansas lab once or twice a week.

Only 3 suspicious spores were on the slide that was sent to the lab by Boyd Padgett, plant pathologist at the LSU AgCenter's Northeast Research Station. The trap was in a soybean field at the station. No infected soybean plants were found in an adjacent soybean field free of ASR symptoms, Padgett said. About 100 spores are required to do the DNA tests for confirmation of ASR.

Finding the spores does not mean soybean plants will necessarily get infected. "That all depends on conditions," Schneider said. He said that moisture is required for an infection to start. If we get regular rain and heavy dews, then the occurrence of ASR is more likely. If the spores are the ones that cause ASR and if conditions are right, it will be about 2 weeks following the spore shower before symptoms of the disease show up."

Because of the early warning that ASR rust had entered the country on the winds of Hurricane Ivan in late 2004, soybean growers, industry people and university experts have been able to prepare to manage the disease, should it develop. The disease, first discovered in Asia in the early 1900s, has steadily been spreading. It also is in Africa and South America, where it has caused devastating yield losses because it spreads quickly, if undetected.

According to Clayton Hollier, LSU AgCenter monitors sentinel plots, which were planted earlier in 2005, and select soybean production fields. "We are alerting growers to continue and increase their scouting efforts," Hollier said. "Growers certainly need to be prepared to spray for ASR."

Besides Louisiana and Arkansas, the other states involved in scouting for ASR are Illinois, Kentucky, Mississippi and Tennessee. "This is a very important find," said Glen Hartman, research plant pathologist with the USDA Agricultural Research Service (USDA-ARS) and associate professor at the University of Illinois at Urbana-Champaign. He's one of the nation's leading experts on ASR, Schneider said. "What it means is that we're forewarned that the disease may be getting a start this growing season," Hartman said. "Scouting must be intensified. If we can get to the R6 growth stage without finding the disease, then we are out of the danger period,"

Asian soybean rust can destroy soybeans through the R6 growth stage, which is when the pods are forming. ASR can't hurt yields in the last 2 stages (R7 and R8), when the beans yellow and the plant is harvested.

[byline: Linda Foster Benedict]

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<promed@promedmail.org>

[This is the 1st report of potentially positive spores being found in the spore traps located in AR, IL, KY, LA, MS, and TN. All spore samples from the traps are being tested in a laboratory established at the University of Arkansas; all others tested have been negative to date. Continued scouting of soybean fields and sentinel plots may provide more information on the status of ASR in the next week or so. The fact that only 3 ASR-like spores
could be found on 1 slide illustrates the difficulty that rust scouts are facing. - Mod.DH]