Soybean Rust Update for 2008

Bob Mulrooney, Extension Plant Pathologist; bobmul@udel.edu

Soybean rust continues to be a threat to soybean production in the US. Although we have not seen it here or in MD yet that does not mean that growers can let down their guard. It is important to continue to track its whereabouts and have an action plan in place should it appear. All it took was some heavy rainfall in LA, TX and OK last season to produce conditions that were very favorable for rust development. The rust spore production in those states was great enough that soybean rust was found late in the season in Iowa. Fortunately, it was too late in the season for rust to have any affect on yields in the northern states. All we would need is for the drought to be broken in northern FL and GA one of these years, and soybean rust could make it to DE and MD. Granted a lot depends on the weather, but the fungus continues to overwinter in southern FL and is infecting scattered patches of kudzu along the Gulf of Mexico at the present time. So it is important to know where it is during the growing season. The ipmPIPE website is still the best place to get your soybean rust info (http://www.sbrusa.net/). For more info and labels of registered fungicides for use in DE see the UD Extension soybean rust website at http://ag.udel.edu/extension/pdc/soybeanrustResources.htm

In 2007 soybean rust was detected in one province in Canada, in two states (3 municipalities) in Mexico, and in 19 states and 334 counties in the U.S including: 40 counties in Alabama (19 soybean), 33 counties in Arkansas (soybean), 24 counties in Florida (11 soybean), 51 counties in Georgia (14 soybean), four counties in Illinois (soybean), one county in Indiana (soybean), 14 counties in Iowa (soybean), nine counties in Kansas (soybean), three counties in Kentucky (soybean), 21 parishes in Louisiana (18 soybean), 26 counties in Mississippi (21 soybean), 37 counties in Missouri (soybean), four counties in Nebraska (soybean), six counties in North Carolina (soybean), 12 counties in Oklahoma (soybean), seven counties in South Carolina (soybean), seven counties in Tennessee (soybean), 26 counties in Texas (25 soybean), and nine counties in Virginia (soybean).

rustmap19mar2008.jpg

As of March 27 there are 10 counties in Florida, two in LA, one in TX, and one in AL with rust on kudzu at the present time. In Mexico there are three counties with soybean rust on another legume called jicama bean. Kudzu is coming out of dormancy in much of the South so rust activity should be increasing in the coming weeks.

Delaware will continue to participate in the ipmPIPE sentinel plot system for detecting soybean rust in a timely manner for the 2008 season. At the present time seven sentinel plots are planned for Delaware, three in Sussex and two each in Kent and New Castle counties. USDA/APHIS and commodity funding is continuing to fund this effort at the present time. Each sentinel plot will be planted with a group III and a group VII variety so that susceptible plants are present throughout the growing season and into the late fall.

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