Integrated Crop Management

Sentinel plots at end of the 2006 season

We are completing our second crop season since Asian soybean rust (ASR) was found in the United States. We can breathe a sigh of relief and give thanks that ASR did not make its way to Iowa. Indeed, this potentially devastating disease has not plagued the entire north-central United States. Had conditions been favorable for this disease, we were ready to give producers fair warning.

The United States Department of Agriculture (USDA) and the North Central Soybean Research Project (NCSRP) funded the establishment of sentinel plots in Iowa and across the midwestern and southeastern United States. Perhaps you have logged on to to watch the national map that shows the results of scouted sentinel plots and locations where soybean rust has been found. This year's warm, dry weather was not conducive to disease development. Nevertheless, rust was found on soybeans in 25 different counties in seven states: Alabama, Florida, Georgia, Louisiana, Mississippi, South Carolina, and Texas by September 8.

Sentinel plot at Castana [1]
Sentinel plot at Castana. Two maturity groups were planted at different times. The difference in plant height is due to different planting dates. Castana was extremely dry during June and July. The plants survived the drought but did not grow tall. (Ralph von Qualen)

Rust did not come close to Iowa, but we remained vigilant because this is a new disease and we could not be certain of its progress.

We are sincerely grateful to those who assisted in putting out Iowa's 21 sentinel plots. They are:

Cooperator Location
ISU Curtiss Research and Demonstration Farm Ames
ISU Western Research and Demonstration Farm Castana
ISU McNay Research and Demonstration Farm Chariton
ISU Armstrong Research and Demonstration Farm Crawfordsville
ISU Muscatine Island Research and Demonstration Farm Fruitland
ISU Neely-Kinyon Research and Demonstration Farm Greenfield
Croplan Genetics Harlan
Croplan Genetics/West Central Cooperative Jefferson
ISU Northern Research and Demonstration Farm Kanawha
Kevin Greiner Keota
ISU Armstrong Research and Demonstration Farm Lewis
UAP Midwest Mediapolis
ISU Northeast Research and Demonstration Farm Nashua
Croplan Genetics New Hampton
Allee Iowa State University Research and Demonstration Farm Newell
Arnie Shirley and Cornerstone Seeds Sidney
Croplan Genetics Sioux Center
Croplan Genetics Slater
Croplan Genetics Springville
ISU Northwest Research and Demonstration Farm Sutherland
Croplan Genetics Webster City

We needed these cooperators to put out the plots, but what made these plots effective was the close monitoring they received throughout the growing season. Trained professionals closely scouted these 21 locations for any signs of rust. We carefully inspected each plot every week. Diseases that were commonly seen in the plots were brown spot, bacterial blight, downy mildew, Cercosopora leaf blight, and frogeye leaf spot. The results of these efforts were regularly posted on the USDA's sbrusa Web site.

Many thanks go to the field crop specialists who added weekly visits to sentinel plots to their already busy schedules. Without their assistance it would have been difficult to scout all the plots. Iowa State University field crop specialists who helped in this regard are Mark Carlton, George Cummins, James Fawcett, John Holmes, Brian Lang, and Virgil Schmidt. Researchers from ISU's Department of Plant Pathology also scouted plots.

We are sincerely grateful to everyone who helped in this important effort.

We also used spore traps to learn whether any spores may have blown into our area.

Iowa's soybeans are no longer at risk for yield loss due to ASR. Nevertheless, researchers continue to monitor spore traps and some late planted long maturity group soybeans to learn whether any spores reach Iowa this fall.

Sentinel plot at Allee Farm [2]
Two photos of the sentinel plot at Allee Farm near Newell, Iowa. Two maturity groups were planted at different times so we could have soybeans at a reproductive growth stage early but continue to have green soybeans late in the season. In addition, rows of maturity group 7 forage soybeans were planted within the plots. In September the regular sentinel plot is approaching maturity, but the forage soybeans are 40 inches tall and just beginning to bloom. (Ralph von Qualen)

This article originally appeared on pages 236-237 of the IC-496(24) -- September 18, 2006 issue.

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