February 26, 2006
From: ProMED-mail<promed@promedmail.org>
In this update:
[1] New finds on kudzu in SW Alabama, 20 Feb 2006
[2] Rust Found on soybean in Texas, 22 Feb 2006.
[3] Rust from Texas, Mexico could fly north in rust corridor

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[1] New finds on kudzu in SW Alabama, 20 Feb 2006
Date: 20 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: sbrusa.net - National Map Commentary (updated: 20 Feb 2006)[edited] <http://www.sbrusa.net/>

Over 40 kudzu patches were scouted for Asian soybean rust (ASR) last week in SW Alabama. One infected kudzu site was found in Mobile County, and 2 infected patches were found in Baldwin County. These patches were situated in protected locations, and rust was only found on old kudzu tissue. Both of these counties had positive rust finds on kudzu in 2005.

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[2] Rust found in Texas, 22 Feb 2006.
Date: 23 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source:
dtnsoybeanrustcenter.com [edited] <http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=65&pid=12>

Asian soybean rust (ASR) has been discovered on soybeans in Hidalgo County, Texas, at the Texas A&M Experiment Station in Weslaco, the United States Department of Agriculture (USDA) reported on Wednesday 22 Feb 2006.

Hidalgo County sits at the bottom of Texas along the Mexico border. The ASR was found in a soybean field that had been planted last fall for research not related to rust. Scouts checked the field for rust in December 2005, but no sign of the fungus was found.

"Apparently it came in sometime in January," said Marvin Miller, the Texas A&M plant pathologist who reported the find after examining a sample brought in by a technician last week. Most of the soybean plants in the field were mature, but some younger plants that had grown along the edge of the field were infected, Miller said.

"This field (about 1 acre in size) will not serve as a source of inoculum, as it has been harvested," Texas A&M plant pathologist Tom Isakeit reported on USDA's rust website. "This field was planted much later than usual.
Normally, soybeans in this part of the state would have been harvested by mid-December," he said. "There are no other soybeans around and there is no kudzu in this area of the state."

Based on wind circulation patterns, experts estimate the chance of ASR spores reaching the Midwest increases nearly 4-fold annually if "the disease establishes itself early in any given season across Texas or western Louisiana, rather than the south east, where it was largely confined in 2005," Dow Jones Newswires reported.

The spores that infected the Hidalgo County, Texas, field could have possibly come from Mexico, Miller said. Last week a Mexican scientist reported that ASR was found on soybeans in the states of Tamaulipas and San Luis Potosi, Mexico, in October 2005. The reports have not been confirmed by the Mexican government, Isakeit said, and the information released was minimal. Tamaulipas, which borders the tip of Texas, is the northernmost Mexican state along the Gulf of Mexico. San Luis Potosi borders the south west corner of Tamaulipas.

"I can't say for sure it came in from Mexico," Isakeit said. "Maybe it blew in directly from South America," but it is sort of falling into place that there was movement in Mexico last year, he said.

Though Texas will be increasing its ASR surveillance, Isakeit said it may be difficult to detect because of the drought conditions. "We might not see it in South Texas because we need rain to bring the spores down (from the atmosphere)," he said.

An ASR sentinel plot for this spring was planted last week in Weslaco.
Multi-purpose soybean research plots will be planted near Corpus Christi this week, which will be monitored for rust, and Victoria County will also be planting an ASR sentinel plot soon.

"I am more concerned about (ASR) than I was last year," Isakeit said. This early find "tells me there is some movement of spores."

[byline: Aine Gianoli <aine.gianoli@dtn.com>]

- Mod.JAD]

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[3] Rust from Texas, Mexico could fly north in rust corridor
Date: 24 Feb 2006
From: ProMED-mail <promed@promedmail.org>
Source: stopsoybeanrust.com [edited]
<http://www.stopsoybeanrust.com/viewStory.asp?StoryID=692>

While scientists are not sure how ASR will behave now that it's in central Mexico and South Texas, some are concerned that fungal spores from here will ride the winds to the Midwest's multibillion dollar soybean crop.
Marvin Miller, a Texas Agricultural Experiment Station plant pathologist in South Texas, found the fungus on soybean leaves on 14 Feb 2006 in a research field plot at the Texas A&M University System Agricultural Research and Extension Center at Weslaco.

A preliminary diagnosis made at the Texas Plant Disease Diagnostic Laboratory in College Station was confirmed by a USDA laboratory in Beltsville MD, Miller said."Soybean production here in South Texas isn't significant, but this is of great concern to the production areas of the Midwest," Miller said. "In addition to soybeans, cowpeas, green beans, and other edible legumes could be affected by this fungus which causes defoliation and yield reduction."

The soybean rust fungus (_Phakopsora pachyrhizi_) was first introduced into the US in Florida in 2004, probably borne by hurricane winds, but confined itself to the south east, according to Tom Isakeit, a plant pathologist with Texas Cooperative Extension in College Station. South Texas rust find is likely to be a new introduction. "This finding in South Texas is probably a new introduction," Isakeit said. "And what it suggests is that soybean rust could take the so-called "rust corridor" to points possibly as far north as Canada." Prevailing winds have been blamed for taking a number of other rust diseases on a northerly path, including southern rust of corn, stem rust of wheat, and common rust of corn, he said.

Joseph Krausz, a scientist at Texas A&M University's department of plant pathology, said confirmation of soybean rust in both Mexico and Texas is very significant. "The recent occurrence of soybean rust in South Texas and in the Mexican states of Tamaulipas and San Luis Potosi late in 2005 may very well be the first step in the pathogen becoming established, or endemic, in the 'rust corridor,' which historically has been the pathway of seasonal dissemination of a number of rust diseases from south to north,"
Krausz said. Environmental conditions will play a major role in influencing the further establishment of the pathogen in the corridor, he said.

The soybean rust found in Texas on Valentine's Day 2006 was in a one-acre research field plot in Weslaco that was part of an irrigation study.
Isakeit had checked the field in December 2005 and found no symptoms of the fungus. "Infection must have happened after my visit in December, unless plants were already infected but were not yet showing symptoms," Isakeit said. Trying to pinpoint the source of the spores can be difficult, he said.

"Rust spores can be carried by wind currents hundreds or even thousands of miles, even across oceans," Isakeit said. "They are eventually brought down to earth by rain, and a leaf that's been wet for several hours is needed in order for a spore to germinate and infect a plant." But once a plant is infected, the fungus can multiply rapidly, Miller said. "That's why growers need to be vigilant. There are fungicides that are registered for use on soybean rust, but early detection and treatment are key," he said.

Resistant varieties of soybeans are being developed, but will not be available to growers for several years, according to the American Soybean Association's website. The field in Weslaco where the fungus was found has been harvested and plowed under, but Miller said a "sentinel" plot of soybeans will be planted to serve as an early-warning system for growers.
"A few rows of soybeans will be planted shortly which we'll be checking throughout the spring," he said.

Isakeit said other bean crops grown in the area, including commercial green bean and cowpea fields, also will be monitored. "Surveying these fields will provide information to get the big picture of how this fungus behaves in this part of the world," he said. "We know it's caused major losses in Asia and other parts of the world, but we don't really know how it will affect crops here. The weather and prevailing winds this spring will play a big role in what happens, but if South Texas bean crops have a rough year with soybean rust, there will be the potential for a bad year further north."

The US is the world's largest producer and exporter of soybeans, with a farm value of USD 18 billion in 2003-04, according to USDA. Soybeans are used in 90 per cent of the total US oil seed production and are grown throughout the Midwest, with the heaviest concentration of the crop in Illinois, Indiana and Iowa.

[byline: Rod Santa Ana III of Texas A&M University AgNews]

--
ProMED-mail
<promed@promedmail.org>

[Asian soybean rust (ASR)is caused by the fungus _Phakopsora pachyrhizi_ and was introduced into the USA in 2004. It was detected in the crop plant soybean (_Glycine max_) at the Texas A&M Experiment Station in Weslaco on 22 Feb 2006. This marks the most westerly detection of ASR in the USA to date. The soybean field has already been harvested, so the infected plants are now gone. It is significant that ASR was detected in October 2005 in adjacent Tamaulipas, which borders the tip of Texas, and is the northernmost Mexican state along the Gulf of Mexico (see map link in item 2). ASR was also detected in October 2005 in the state of San Luis Potosi, Mexico, which borders the southwest corner of Tamaulipas (see map above in item 2). This has led to discussion that these adjacent centers may become an annual starting point for future epidemics of ASR, following the "rust corridor" through southern, midwestern, and northern states in the USA and also Canada. In addition to soybeans, cowpeas, green beans, and other edible legumes could be affected by the ASR pathogen, which causes defoliation and yield reduction. Rust diseases of cereals caused by _Puccinia_ spp. are examples of diseases that progress through the rust corridor each year (see map below). The observations made in Weslaco, Texas this week would become a landmark in the history of ASR in the USA were this to happen.

ASR infections on kudzu were found in 2 additional counties in SW Alabama this week. The confirmed reports of ASR in 2006 now include Texas with one, Alabama with 3 and Florida with 11 counties as of 23 February 2006.

Maps:
Asian soybean rust outbreaks 2006 <http://www.sbrusa.net>
The wheat rust corridor <http://ars.usda.gov/images/docs/9757_9951/puccini_path.gif>
Pictures
<http://www.dtnsoybeanrustcenter.com/index.cfm?show=65&mid=60&page=ALL>
Diagnosis cards (broadband best)
<http://www.aphis.usda.gov/lpa/issues/sbr/SBR_IDcard_11-04.pdf>
Links:
National commentary, updates from states, maps, chronology <http://www.sbrusa.net>
Latest news, articles, maps and tracking information <http://www.stopsoybeanrust.com/mc_home.asp>
Latest news, articles and other information <http://www.dtnsoybeanrustcenter.com/index.cfm?show=10&mid=31>
More links on ASR: <http://www.stopsoybeanrust.com/mc_resources.asp> - Mod JAD]

[see also in the archive:
Soybean rust, Asian strain update 2006 (02): USA 20060221.0568
Soybean rust - Mexico: 1st report 20060219.0546
Soybean rust, Asian strain update 2006 20060214.0482 Soybean rust, Asian strain - USA (GA) 20060208.0415 ProMED-Plant Disease Report: July - December 2005 20060201.0331
2005
---
Soybean rust, Asian strain - USA: 2005 disease summary 20051228.3694 Soybean rust, Asian strain - USA (KY)(02): confirmed 20051219.3640 Soybean rust, Asian strain - USA (multistate) (10) 20051218.3628 Soybean rust, Asian strain - USA (KY): 1st report 20051123.3404 Soybean rust, Asian strain - USA (multistate)(09) 20051101.3187 Soybean rust, Asian strain, kudzu control 20051006.2914 Soybean rust, Asian strain - USA (GA)(05) 20051005.2902 Soybean rust, Asian strain - USA (AL)(04) 20050917.2743 Soybean rust, Asian strain - USA (multistate)(08) 20050913.2711 Soybean rust, Asian strain - USA (multistate) (07) 20050909.2672 Soybean rust, Asian strain - USA (GA) (04) 20050905.2623 Soybean rust, Asian strain - USA (multistate)(04) 20050829.2556 Soybean rust, Asian strain - USA (GA)(03) 20050827.2531 Soybean rust, Asian strain - USA (AL)(03) 20050826.2528 Soybean rust, Asian strain - USA (AL)(02) 20050824.2496
Soybean rust, Asian strain - USA (SC) 20050818.2414
Soybean rust, Asian strain - USA (FL)(03) 20050815.2386 Soybean rust, Asian strain - USA (Multistate)(06) 20050808.2318 Soybean rust, Asian strain - USA (multistate)(05): susp. 20050806.2291
Soybean rust - USA (multistate)(04) 20050806.2289
Asian soybean rust, Asian strain - USA (multistate) 20050724.2133
Soybean rust, Asian strain - USA (AL) 20050715.2029
Soybean rust, Asian strain - USA (multistate)(03) 20050714.2005 Soybean rust, Asian strain - USA (multistate)(02): Florida 20050708.1938 Soybean rust, Asian strain - USA (multistate) 20050702.1868
Soybean rust, Asian strain - USA (LA) 20050624.1769
Soybean rust, Asian strain - USA (FL) (02) 20050620.1731
Soybean rust, Asian strain - USA (GA) 20050505.1245
Soybean rust, Asian strain - USA (GA) 20050429.1196
Soybean rust, Asian strain - USA (FL): 1st report 2005 20050309.0693]