Asian soybean rust has been found on soybeans in the western-most U.S. location yet -- Weslaco, Texas, in Hidalgo County, just a few miles north of the Mexican border. The field was harvested Feb. 14, so it won't serve as a source of inoculum, officials said.

In today's Texas state commentary, Texas A&M Extension plant pathologist Tom Isakeit reported the rust was found on soybeans growing in a one-acre field at the Texas A&M Experiment Station in Weslaco. He had surveyed the field in December 2005, but did not see any symptoms of rust then.

On Feb. 14, the find was reported by plant pathologist Marvin Miller after he examined a sample brought in by his technician Robert Saldana. On Feb. 16, the finding was confirmed with an ELISA test by Larry Barnes of the Texas Plant Disease Diagnostic Clinic. Official USDA confirmation came today, after testing at the USDA-APHIS laboratories of this first find in Texas on soybeans. John McKemy ran the morphology and Laurene Levy confirmed the presence of Asian soybean rust using PCR (polymerase chain reaction) techniques.

The same day the sample was pulled, the field was being harvested, Isakeit said, noting that it therefore "will not serve as a source of inoculum, as it has been harvested."

"Dr. Miller reported that rust was quite prevalent on plants that were at the ends of the rows," he said. "These plants were a little less mature than the rest of the crop."

Isakeit also said the field was planted much later than usual. "Normally, soybeans in this part of the state would have been harvested by mid-December."

There are no other soybeans around, he said, and the soybean sentinel plot in Weslaco was planted just last week. There is no kudzu in that area of the state, he said.

Isakeit told fellow soybean rust specialists that the prognosis "depends upon the weather in the spring. This is a situation where the sentinel plots in south Texas will really prove their worth."

As to the origin of the Hidalgo County rust, Isakeit told that it is possible that it came up the so-called "rust alley" from Mexico, either off of soybeans down there or perhaps other legume hosts. There also could have been a direct introduction from South America, he suggested.

Last week, Mexico reported that soybean rust was found in October 2005 in the state adjacent to Hidalgo County -- Tamaulipas. The Mexican city near which the rust was found -- Altamira -- is approximately 260 miles south of Weslaco, where the Texas rust was just reported.

There are now 17 U.S. counties where soybean rust has been confirmed in 2006. Hidalgo County is the first in Texas this year. Last year, the only confirmed soybean rust in Texas 330 miles to the northeast -- on kudzu in the southeast Texas county of Liberty, north of Galveston.