Scouting for soybean rust, primarily on kudzu, continues in the southern states. Kudzu is beginning to green up across the southern United States and scouting efforts in those areas has intensified. Thus far, soybean rust has been confirmed on kudzu in eleven Florida counties, four Georgia counties and five Alabama counties as well as on soybean plants (since harvested) in one Texas county. As of April 3, 2006, there have not been any reports of soybean rust on newly planted soybeans. Sentinel plots have been planted in many of the southern states and some are beginning to emerge. The USDA Public Soybean Rust Web site at www.sbrusa.net is being updated on a regular basis, and is a good source for information on reports of soybean rust in the southern United States.

Missouri will be participating in the sentinel plot program again this season. However, this early in the season, none of our sentinel plots have been planted, kudzu is still dormant and scouting (except for observations on kudzu growth) hasn’t begun.

It will be particularly interesting and important to follow reports from Texas and Mexico during the 2006 season.

Texas: The soybean rust pathogen was confirmed on kudzu leaves collected from a site near Dayton, Texas (just northeast of Houston in Liberty County, Texas) on November 2, 2005. Soybean rust was not found in soybean fields near this kudzu patch. And on January 17, Tom Isakeit, Extension Plant Pathologist with Texas A & M University, reported that the kudzu patch in Liberty County had been completely killed back. Then in February of 2006, soybean rust was confirmed on plants in a one-acre plot in Weslaco, Texas (Hidalgo County just north of the Mexican border). The plot was part of an irrigation study, and most of the plants in the field were mature by February 14. Soybean rust was found on some younger plants along the edge of the field. The plot was harvested not long after the rust was confirmed. At this point the kudzu in Dayton, Texas (Liberty County) has been developing new growth but has not shown symptoms of soybean rust on the foliage. Sentinel plots that have emerged have not shown any symptoms of soybean rust.

Mexico: In February it was announced that soybean rust had been confirmed on leaves collected in October 2005 from the variety Huasteca 400. The leaves were collected at harvest and had symptoms and signs of a low incidence of soybean rust. Confirmations of soybean rust on soybeans were made from two locations, Tamuin in the State of San Luis Potosi and Altamira, in the state of Tamaulipas (northeastern part of Mexico). Samples were collected as the fields were being harvested and there have not been additional reports of soybean rust from Mexico.

Again, for 2006 it is important for soybean producers in Missouri to be aware of disease development and weather patterns in the southern United States; to scout fields and be aware of results from the sentinel plot system in southern states, states close to Missouri and in Missouri; and to be prepared to take prompt action if a risk of soybean rust develops.

Laura Sweets
Ag Ext.-Plant Sciences
573-884-7307