Interpreting fungicide information has certainly gotten a lot more complicated than it used to be. To date, using foliar fungicides in soybean production in central Illinois has been virtually non-existent.

The introduction of soybean rust to the southeastern United States has changed the fungicide use outlook dramatically. Before you invest any money in fungicides for the upcoming production season though, let’s be clear about some significant legal and economic issues.

First let’s jump into the legal issues. As you have heard me say at Pesticide Safety Training and testing sessions over the past years, the label for a pesticide is a legal document. That means regardless of if the pesticide is a general or restricted use product the applicator is obligated to follow the label. Fungicides that have a full legal label for use are described as having a Section 3 label. In Illinois we actually have had very few fungicides that have a Section 3 label for use in soybean for control of fungal leaf or stem diseases. A list of these fungicides can be found in the 2007 University of Illinois Agricultural Pest Management Handbook. They are azoxystrobin (Quadris), chlorothalaonil (Bravo and numerous brands), thiophanate-methyl (Topsin-M) and pyraclostrobin (Headline).

Why am I bringing this issue up? Well, when soybean rust was identified in the U.S., numerous states applied for emergency use permits for triazole and triazole/strobilurin combination fungicides to control soybean rust. This kind of emergency label is called a section 18. The EPA granted numerous section 18’s for these states including Illinois, thus allowing the use of those products “in soybean, specifically for management of soybean rust”. For the most part the section 18’s have been granted through November 2007. During the interim the EPA would expect that company’s who have been granted section 18’s would go through and complete the process to apply for full section 3 labels.

So we find ourselves in a bit of an awkward situation. As soybean rust gains momentum in the south we are well aware that the probability of in season infection for Illinois increases. Growers want and need information on these section 3 and section 18 fungicides relevant to Illinois conditions. As a result, researchers and pesticide industry folks initiated research to look at the effect of these many products on soybean rust. The research went forward regardless of the fact the soybean rust did not impact Illinois in 2005 or 2006. Information gleaned from these studies can be confusing. Some of these products did economically manage current diseases we have in Illinois, some treatments however resulted in economic loss, and some of the treatments were break-even economically. This is interesting from the point of view of managing current Illinois fungal diseases. However, you must exercise caution in adapting these findings to your soybean production. Prior to the actual identification of soybean rust in Illinois in a given season, the only fungicides you can legally use to control fungal diseases are the section 3 products I’ve mentioned above. If you have purchased any of the section 18 fungicides in anticipation of soybean rust, that means you’ll be storing them until soybean rust is positively identified in the state, because you can’t legally use them to control other diseases in soybean.

By SUZANNE BISSONNETTE, Pest Magement Educator
UI Extension Office
Suzanne Bissonnette is an integrated pest management educator for the University of Illinois Extension.

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