Crop Updates / News and Information
| 06/24/05 | Spores of Interest Found at St. Joseph Research Station
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| Submitted by: Clayton Hollier, Ph.D.
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| Three (3) rust spores with features resembling P. pachyrhizi, causal agent of Asian soybean rust (ASR), were found in a spore trap near St. Joseph, LA. Although they closely resemble spores of the ASR pathogen, there has been no confirmation nor can there be with these spores that were found on a slide from a spore trap. It is possible that spores of other rust fungi have similar features, and microscopic examination cannot differentiate among these other species. It is extremely important to not be alarmed by this finding!!! No Asian soybean rust has been found in the fields adjacent to the spore trap!!! No ASR has been found in Louisiana or surrounding states!!! However, if this is the ASR pathogen, it is possible that the disease may develop soon at which time alerts will be disseminated by appropriate means. The reason for this communication is to alert the industry about this finding; however, this is not a confirmation of ASR in Louisiana. Because of the uncertainty with this sample, all those involved with scouting for ASR should double their efforts and look even more diligently in soybean fields throughout the state. Q and A’s 1. Do fungicide applications to soybeans for rust protection need to commence? There is no indication of the beginning of an epidemic of ASR at this time. Factors that need to be considered in the decision to spray include: a) wet weather will increase chances of rust development if rust spores are present in the crop; b) the growth stages are very important in that the reproductive stages need to be protected through R6; c) are there other diseases developing in the field? If a grower is applying fungicides for the cercospora diseases, then a tank mix or pre-mix to take of cercospora and rust may be prudent. Please refer to the fungicide list on the LSU AgCenter rust website for details of appropriate products and combinations. 2. How and where were the “spores of interest” found? Three (3) “spores of interest” were found in a spore trap sponsored by Syngenta Corp. and managed by Dr. Boyd Padgett, near St. Joseph, LA. The glass slides from these traps are sent to Dr. John Rupe at the University of Arkansas for microscopic detection of any ASR spores. These three are the only rust spores found and it is not certain that they are ASR spores. 3. What does this finding mean for our soybean growers? More than anything else, this finding means that scouting of ASR should not only continue but intensify.
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