Monday, August 28, 2006

Weekly Soybean Rust Update

from the Illinois Soybean Rust Information Center~

Crop Growth Stage
Across the state sampled sentinel soybean plots are all in the reproductive stages ranging from R5 to R6.

Observation and Outlook: Experimental spore traps
No spores or rust-like spores detected in the Illinois experimental spore traps in the last week. Previously, spores resembling those of soybean rust were detected in the Illinois Syngenta rust traps the week of August 14. These positive traps were in 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.

Observation and Outlook: Sentinel plots
No soybean rust to report in Illinois. Thirty nine sentinel soybean rust plots (one plot has been harvested--pea plot) are being sampled for soybean rust in the state , most plots are soybean but kudzu is also included. The field pea plot has been harvested. Additional legumes in sentinel plots include dry beans, Phaseolus vulgaris, and mung beans, Vigna radiata. Double crop soybean sentinel plots have been planted in southern Illinois. Additionally, 16 of the sentinel plots are being scouted for soybean aphid for the PIPE program.

Several foliar diseases are being observed including Septoria brown spot,frogeye leaf spot, bacterial blight, bacterial pustule and downy mildew. Rust was not observed.

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

Sentinel plot pre-screening leaflet samples are being received and analyzed by the University of Illinois Plant Clinic. The above diseases were all confirmed. No soybean rust was detected.


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