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First rust-like spores of 2006 trapped in Texas, Syngenta site says
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By Marilyn Cummins, Editor
StopSoybeanRust.com
5/25/2006 -- Last night, Syngenta posted on its Web site a report of 30 suspected soybean rust spores caught on a slide from a Syngenta Syntinel(TM) spore trap in Beasley, Texas, in Fort Bend County.
No commentary accompanied the spore count data as of early this morning. [Update 5/26/2006 -- see Syngenta commentary.]
It’s important to note that the spores are only "suspected," and to remember that USDA and rust experts (including at Syngenta) say not to read too much into even "positive" or "confirmed" reports of rust spores trapped in this or other manners. Finding rust-like spores in the trap doesn’t mean there’s a rust infection in or even near Beasley.
"Our whole goal in collecting spores is to be able to say 'now it's time to scout,'" if weather is conducive to spores infecting soybeans and other hosts in an area, Marty Wiglesworth, Syngenta technical fungicide brand manager, told StopSoybeanRust.com in a recent interview. "It's more of a heads-up kind of thing."
This is the first such report of rust-like spores captured in 2006. In the same spore-trap report on the Syntinel(TM) RustTracker site last night, Syngenta said no spores were found on slides taken from three other traps located in Burleson County, Texas, (a few counties northeast of Fort Bend); and in Catahoula and Franklin counties in Louisiana. Syngenta is in the early stages of putting some 148 traps in place this year, starting south and working north, most in conjunction with state sentinel plot systems.
Suspected spores not far from last year's Texas rust
Beasley, where the suspected spores were trapped on the southwest side of Houston, is about 300 miles northeast of the only rust-infected plants found (and destroyed) in Texas so far this year -- on a few old-season soybean plants about to be harvested in late February in Hidalgo County.
The location of the trap in question is, however, a mere 85 miles southwest of the only place known to have soybean rust in Texas last year -- outside Dayton, in Liberty County, where rust was found growing on leaves in pretty much the only known kudzu patch in the county.
Syngenta uses solid green, yellow and red triangles on its RustTracker spore trap network maps to denote Syngenta-not-found rust spores; Syngenta-suspected rust spores and Syngenta-confirmed rust spores.
Spores don’t mean rust is present, but can precede infections
In its online help file about the tracking system, Syngenta says the spore traps "act as a guide to determine when rust scouting should intensify in fields and sentinel plots." Growers are cautioned that if a spore trap sample is deemed to be “positive” for soybean rust spores, that doesn't necessarily mean that the disease is in the area.
Slides from all Syngenta-supplied traps are sent to plant pathologist John Rupe at the University of Arkansas for processing and microphotography; he then distributes pictures of the captured spores to rust experts for visual identification. If a consensus is reached that the spores match killed rust spores or photos of known Asian rust spores based on size, surface ornamentation and pigmentation, the sample is considered positive.
Because of the low number of spores on any one slide, no means of 100-percent confirmation is available in this system.
Wiglesworth said that in analyzing last year's tracking results, soybean-rust-like spores were found in 13 states and in 61 percent of the traps in place (59 sites). They looked at what happened after spores were found, and determined that where rust did develop in Alabama and Georgia, symptoms became visible an average of 31 days after spores were trapped in that area.
USDA says spore traps useful, with caveats
After news of spores found in various areas last year triggered some confusion, rumors and reported overly aggressive local salesmanship by some parties, USDA issued a position statement on "Phakopsora pachyrhizi Urediniospore Trapping." In its summary, it said:
"USDA believes spore trapping could prove useful in future surveys and modeling efforts; however USDA also believes there are many challenges and questions that need to be resolved before spore data can be used most effectively. Therefore, spore trap observations need to be put into the context of what is known about ASBR epidemiology and observed behavior in the United States."
The USDA statement says one objective of spore trapping is to help give an early warning to scout, based on state specialist direction. Other goals over time are to help validate the aerobiological model used to predict spore movement and deposition; to compare the period between spore trapping and disease development with the intervals predicted by models; and to provide spore-quantity data for the model(s) that estimate spore production and/or spore dispersal.
Source: Syngenta spore trap data on www.soybeanrust.com; USDA position statement; StopSoybeanRust.com interviews and archives.
Related stories from our 2005 archives:
6/16/2005 -- More states report spore traps in place to detect rust
6/22/2005 -- Rust-like spores found in LSU spore trap near St. Joseph, LA. See links to commentary from other state specialists at bottom of LSU story.
6/23/2005 -- Syngenta discusses spores found in LA Syntinel(TM) spore trap.
7/8/2005 -- Photograph of spore trap helps explain how researchers are finding spores.
7/11/2005 -- "Ten spores not enough" to determine, spread soybean rust
8/19/2005 -- Illinois traps rust-like spores in four counties this week.
For an easy way to stay informed, sign up for the weekly Bulletin e-mail newsletter from www.StopSoybeanRust.com. You also will receive our RUST FLASH e-mails alerting you to important breaking news as soon as it occurs. All are archived in Bulletins.
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