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Asian soybean rust found on kudzu in Liberty County, Texas

Asian soybean rust has overwintered in a known infected patch of kudzu under a bridge in Liberty County, Texas, officials report. It becomes the 23rd U.S. county or parish with rust this year.

In commentary posted late Saturday and updated again Sunday on www.sbrusa.net, Texas officials said rust was found on kudzu under a bridge north of Dayton.

"Rust was found in this location last fall, and the kudzu had died back over the winter. The incidence of rust was low," the report said. "The incidence of rust was a few leaves in an area of approximately 2,500 sq. ft. There was no rust on leaves on vines that had grown beyond the bridge. There was no evident rust on kudzu at the other location in Dayton, nor was there rust on kudzu in Livingston, to the north of Dayton. Both sites had rust in the fall of 2006."

Also in the update, officials noted that "commercial soybean crops in south Texas are flowering to full pod. Many fields will soon no longer be vulnerable to yield loss if rust appears."

The state soybean rust coordinator put the find into perspective, saying, "The recent finding of rust on a small kudzu patch in East Texas should not be regarded as a threat to commercial soybeans in Texas or other states. This finding may indicate overwintering, but the small amount of rust and its location in relation to most of commercial soybeans in Texas does not represent a significant source of inoculum, in my opinion.

"Commercial fields should continue to be scouted, but I am not recommending preventative fungicide applications for rust at this time."

So far this year, soybean rust has been reported in 23 counties and parishes in five states: 10 in Florida, five in Alabama, five in Georgia, one in Louisiana and two in Texas. Only nine counties are shown as currently positive on the USDA rust observation map: Liberty County, Texas; Iberia Parish, Louisiana; and these seven Florida counties: Alachua, Duval, Hernando, Marion, Miami-Dade, Pasco and Sumter.

Until Tropical Storm Barry formed in the Gulf this weekend and cut across central Florida yesterday with heavy rains, Florida's dry conditions had been described this way in the state's May 30th USDA commentary:

"It is still very dry and Florida is still burning. We have had some scattered rains but the soil is dry and leaf moisture from dew is still limiting. The forecast is for continued dry weather. The kudzu is growing rapidly and in those sites that are infected the rust is progressing slowly.

"At present there is no observable rust in the panhandle of Florida. Last week a kudzu site in Marion County in central Florida that was positive last year and earlier this year was found again to be positive. Thus far, we have found fewer positive sites than in previous years."

Now, however, the weekend's storm has brought heavy rains and strong winds to Florida, Georgia and the Carolinas. Rainfall totals in Florida had reached up to seven inches by this morning; up to nearly six inches in parts of Georgia.

Georgia's most recent commentary (5/30) reports that while there is no active Asian soybean rust known to be growing anywhere in the state on soybeans or kudzu, a spore trap in at the Plains Station in Sumter County did produce a sample May 8 that included "soybean rust-like spores."

State soybean rust coordinator Bob Kemerait put the find in perspective in an e-mail sent to county Extension agents and posted in the state commentary, saying in part:

"So what do we make of this?
  1. The spores look like soybean rust spores, but may be from some other rust. This is quite possible, and only PCR analysis (if possible) could confirm the identity.
  2. The spores may actually be Asian soybean rust spores, which would not be too surprising to any of us.
  3. How concerned am I? I am very interested in the image, but not overly concerned, as we have found spores like this in the past. Given that we have extremely dry conditions and also our crop is not yet in reproductive growth, there is no cause for alarm. It is my belief that the detection of soybean rust-like spores simply gives us another reason to monitor for rust, which we do very carefully. However, until we find Asian soybean rust in the field or sentinel plots, we will NOT base any fungicide recommendations simply on the detection of spores. Remember: Spores do not equal Asian soybean rust disease!"

Asian soybean rust has overwintered in a known infected patch of kudzu under a bridge in Liberty County, Texas, officials report. It becomes the 23rd U.S. county or parish with rust this year.

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