Soybean Rust Update- July 10, 2006
By Laura Sweets

Soybean rust has been moving quite slowly in the southern United States. As of July 10, the USDA Public Soybean Rust Web site reported that soybean rust has been confirmed from 25 U.S. counties in five states. Most of these finds are on kudzu and many occurred early in 2006. Over the last week there have been several new finds on kudzu as well as three reports from soybean samples collected from sentinel plots. See the USDA Web site at www.sbrusa.net for exact locations and further information. The breakdown by state is as follows:

Florida
Soybean rust was confirmed in early to mid-January on kudzu in Gadsen, Alachua, Duval, Hernando, Hillsborough, Leon, Marion, Pacso, Lee and Polk Counties. In February, soybean rust was confirmed on kudzu in Miami-Dade. On May 16 soybean rust was confirmed on soybeans in a sentinel plot in Martin County.

Georggia
Soybean rust has been confirmed on kudzu from three counties, Thomas, Brooks and Miller. Soybean rust has just been confirmed on a soybean sample submitted July 3 from a sentinel plot in Decatur County. One of one hundred leaflets in the sample was infected with 7-8 pustules on the infected leaflet.

Alabama
Soybean rust has been confirmed on kudzu in 5 counties (Montgomery, Baldwin, Mobile, Henry and Houston Counties) and on soybeans in a sentinel plot in Baldwin County (June 29, 2006).

Mississippi
Soybean rust has not been confirmed in Mississippi yet this season.

Louisiana
Soybean rust has been confirmed on kudzu in two counties- the Lafayette County positive was found on June 29 and the Iberia County positive was found on July 7.

Texas
Soybean rust was confirmed in a soybean planting in Hidalgo County, Texas on February 12 but that site was harvested shortly thereafter.

In Missouri we have been monitoring samples from 23 sentinel plots located throughout the state. Samples of 100 leaflets/plot were collected every other week through the vegetative stages of growth. As plants moved into reproductive stages of growth sampling has been on a weekly basis. Thus far, all samples from Missouri have been negative for soybean rust. The risk of soybean rust in Missouri is very low at this time. Although scouting of fields, especially as they move into reproductive stages of growth is recommended other control measures are not warranted at this time.

A reminder on foliar fungicide use on soybeans would be that several chlorothalonil formulations (various trade names), Headline and Quadris do have full federal registrations and are labeled for use on soybeans for a number of diseases in addition to soybean rust. The section 18 fungicides have quarantine exemption labels for use on soybeans only if there is a threat of soybean rust and only for management of soybean rust. The section 18 fungicides are not labeled for general plant health or for control of other soybean foliage diseases.

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