Wednesday, October 25, 2006

Weekly Soybean Rust Update

From the Illinois Soybean Rust Information Center (

Crop Growth Stage: Across the state sentinel soybean plots are mature and being harvested. Double crop beans and a few late maturity group bean fields are still somewhat green.

Observation and Outlook: Sentinel plots
On October 10, suspect leaf samples from the Dixon Springs Station in Pope County were sent by overnight express mail to the University of Illinois Plant Clinic. On October 11 at 10 AM, the Dixon Springs leaf samples were observed to have soybean rust and were immediately sent to the USDA Beltsville, MD facility for genetic confirmation. On October 13th, the Director for the Department of Agriculture in Illinois was informed that the leaf samples were positive for soybean rust and a public announcement was made at 10:00 am.
On October 12, two mobile scouting groups were deployed and surveyed soybean fields in the southern part of the state and collected leaf samples from Edwards, Gallatin, Jasper, Johnson, Massac, Saline, White, Alexander, Franklin, Jackson, Johnson, Pulaski, and Union Counties.

Soybean rust has been comfirmed in the following Illinois Counties: Alexander, Hardin, Jefferson, Johnson, Massac, Pope, Pulaski, and White.

Confirmation of soybean rust at this time during the growing season has no consequence for the 2006 crop.

Other hosts will be monitored through the winter to check for any green tissue that may survive and provide a living host for soybean rust.

For the 2006 growing season, forty sentinel soybean rust plots were sampled for soybean rust in the state--most plots are soybean but kudzu and one pea plot were also included. Double crop soybean sentinel plots were planted and scouted in southern Illinois. Additionally, 16 of the sentinel plots were scouted for soybean aphid for the PIPE program.

Several other foliar diseases were monitored and Septoria brown spot, frogeye leaf spot, bacterial blight, bacterial pustule and downy mildew were also observed during the 2006 growing season.

Kudzu plots in southern Illinois show no symptoms or signs of rust infection.

Observation and Outlook: Experimental spore traps Since October 1, spores resembling soybean rust were detected in Syngenta traps in DeKalb, Warren, and Champaign Counties. In late August, spores resembling soybean rust were detected in Illinois experimental spore traps (Warren County, Syngenta trap, 1 spore and Sangamon County, Syngenta trap, 16 spores). Previously, spores resembling those of soybean rust were detected in the Illinois Syngenta rust traps the week of August 14 (Adams County--3 spores, DeKalb County--7 spores, Champaign County--7 spores, Sangamon County--2 spores, and Warren County--12 spores). The first detection of spores resembling soybean rust in Illinois occured in late July in Champaign County. This spore detection method cannot determine if these spores are viable or if these spores are soybean rust spores, Phakopsora pachyrhizi.

Soybean growers should scout their soybean fields once to twice a week and continue to monitor Illinois weather conditions that may be conducive for disease development. Dry to very dry conditions have prevailed in the spore source regions in the southern states and movement of soybean rust to new areas has been slow.About 28 experimental spore traps have been set up in Illinois. These include the Super Sniffers, Windsocks, and Passive Rain Water traps. Although these spore traps can capture soybean rust spores, and samples can be analyzed by various means including microscopic and molecular, these experimental traps cannot distinguish between living and dead spores. Thus, identification of spores in traps does not suggest that rust is eminent but does indicate that weekly scouting is needed.


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