Early-Season Soybean Rust Situation

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

While we are a long way from dealing with soybean rust (SBR), it is still a major threat to soybean production in the South. The incidence of SBR in the last two years has been low to almost non-existent (last season). However 2012 is looking different possibly. We have had a record warm winter which extended to the deep South as well where soybean rust has to overwinter on other live hosts, primarily kudzu. In 2012 soybean rust has been found in Cameron County, TX, Baldwin County, AL, Iberia Parrish, LA and now the most recent find has been in Gadsden County, FL. This is the northern panhandle region where most of the soybeans in FL are grown. The Florida find is the earliest (March 22) that soybean rust has been detected on kudzu in FL. Besides the warm weather, they have had much more rain than in previous years, which has also favored the fungus. The panhandle of FL has only had 70 hours below freezing all winter compared to most years when they see more than 200 hours each winter. The early season is promoting early kudzu growth which could mean increasing levels of rust on kudzu that moves to soybeans that produces spores that have the potential to blow north in storm fronts, tropical storms and hurricanes.

I am not predicting anything here, because it is way too early, but the scenario is developing that we have the potential for soybean rust increasing after record low levels of the past two years. One year the South had a late freeze that killed the kudzu and the fungus along with it, which greatly slowed and reduced soybean rust that year. You can’t predict what will happen, but the forecasters do not forsee that happening this year. If you want to keep up with soybean rust development the ipmPIPE (http://sbrusa.net) is continuing this year despite reduced federal funding Thanks to industry partners, the website will continue for 2012.

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