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Soybean Rust Trying to Make
Move in Louisiana and Texas!

Author: Albert Tenuta - Field Crop Pathologist/OMAFRA Ridgetown
Creation Date: 22 June 2007
Last Reviewed: 22 June 2007

Commercial and sentinel plot soybeans infected with Asian soybean rust have been recently confirmed in Louisiana (June 21) and Texas (June 22). This was not unexpected since for the past month we have been concerned about kudzu infections in south central Louisiana (Iberia and St. Mary's parish). Wind patterns and simulation models suggested that these coastal Parishes could be a source of spores for other regions if weather conditions became favourable. May and June conditions in Louisiana were conducive to potential disease development and the subsequent identification of soybean rust in a soybean sentinel plots in Rapides and Avoyelles Parishes, which are 80 miles north of the rust infected Kudzu, was therefore expected.

In Texas, soybean rust was found Wednesday (June 20) in a 40-acre commercial soybean field 40 miles southeast of Brownsville (Cameron county) that did not have rust when scouted in 2005 and 2006.

This followed the June 14 find in commercial soybeans in Hidalgo County, Texas. The reports of rust occurrences to date are similar to last year with some exceptions of earlier reports of rust in Louisiana and in Texas on commercial soybean fields. These finds put the U.S. count at 26 counties and parishes in five states to have rust at some point in 2007: Florida (10), Alabama (5), Georgia (5), Louisiana (4), and Texas (3).

What Does This Mean To The Ontario Producer? The risk level is still low for Ontario due to the limited soybean rust spore production (to date) in the southern US and the dry conditions in some parts of the province. It is a different situation in Louisiana where the weather conditions are favourable and if the weather continues to cooperate could lead to more rust infections over the next month. This could have implications for Ontario producers since a build-up of spores in the south could make there way into the US mid-west and Ontario. But time is on our side since it will take some time for this to develop but it can occur as witnessed last fall.

One thing is for certain, other soybean rust detections will occur this summer and fall. To what degree will depend on the weather conditions from here on. If things remain favourable in Louisiana that may occur earlier and have a larger geographical impact but if it remains dry over most of the southern US the geographical impact will be minimal as last year ("too little, too late").

Asian Soybean Rust Update Including New Infectons in Louisiana and Texas

Figure 1. Asian Soybean Rust Update Including New Infectons in Louisiana and Texas

Soybean rust updates will continue to be included in future CropPest Ontario issues and the OMAFRA CropLine (1-888-449-0937). You could also visit the Ontario Soybean Growers Website and the USDA PIPE website for updated maps and commentaries.

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