Soybean Rust Update

by Tom Allen

November 3, 2008

I've waited a few days to send this. For the most part we are done scouting for soybean rust for 2008. We did find soybean rust in Marion County on Tuesday in some R7 soybeans. However, as a broader view for 2008, I think we can safely say that we escaped almost completely unscathed with regards to soybean rust for the soybean season. We are essentially 95-98% harvested depending on where you are in the state. The youngest soybeans I've seen are still around Natchez and those beans are moving quite fast to finish the season. If you don't factor in any additional fungicide applications that might have been applied in response to a rust identification I don't think we lost a single bushel to soybean rust this year. That's 4 years in a row. NO yield losses (bushels/A) to soybean rust.

Stats for the year, to this point:

-79 positive counties (rust was not found in Hancock, Harrison or Stone counties) - This is a first for any state. However, I want you to remember that we had soybeans in 77 counties this year and we found rust on soybean in 76 of those. The other three counties had rust on kudzu, however, Wilkinson County had rust on both kudzu (first identification) and on soybeans (verified this past Tuesday). Hancock County was the only one with beans that we couldn't find rust in. Beans were harvested early in this county. This is also the highest number of positive counties we've had to date, and one county more than 3 times what we had in 2007. This goes with the question, are we better at scouting for rust, or is there just more rust out there? I can safely answer there is MORE rust out there. This is certainly the case in the southeast this year. There has also been more rust in AL (2007=40, 2008=56 to date), Louisiana (2007=21, 2008=30), Arkansas (2007=33, 2008=45), and South Carolina (2007=7, 2008=16). But, with that said, there was less rust in some other states GA, TN, TX, OK, KS, IA, GA, and VA just to name a few.

-first time we've ever found rust on soybeans younger than approximately R5.5 in MS. We had two firsts for 2008, rust on R3/R4 soybeans and rust on V-stage soybeans. This is the second time that rust has been reported on V-stage soybeans in the US, and the first time outside of GA (that I am aware of). Essentially, soybeans are tolerant to rust (or more tolerant to rust) in the V-stages. However, if there is a large amount of inoculum present in the area then beans can become infected. I've found this in two locations this year, on volunteer soybeans.

-unfortunately this is also the first year that we've found rust on commercial beans prior to rust in a sentinel plot. However, this is due to our late planted soybean crop and also the later planted sentinel plots. Sentinel plots were planted a lot later this season than in season's past simply due to the weather. The sentinel locations will essentially remain the same next year although there are a few things we may tweek later this winter before we choose locations.

-rust found in Maryland. This is the farthest east that soybean rust has ever been detected in the US, and the first time it's been found in Maryland. The plot with rust in Maryland is right across the border with Delaware. The plot was managed by Delaware and the Delaware group didn't realize that it was in Maryland.

-first year that we have found rust in two consecutive years in kudzu patches in MS. There are still a few locations in the Delta that I need to check that were positive last year, but this is just to build a database of susceptible kudzu locations. Wilkinson, Pike, and Jones County (if I'm not mistaken) all had kudzu patches that were infected for the second year in a row. This is just an interesting tidbit of information and helps us determine those susceptible kudzu locations. We mark those as ones that we continue to check throughout the year and they are essentially a kudzu sentinel plot for the next season.

-1,207 unique locations scouted in all 82 MS counties. The breakdown went like this: 542 kudzu, 658 soybean, and 7 coral bean. I'm still collecting information and this number may likely go up but that's the most we've scouted in a single year. This is partly due to some new soybean fields grown in locations that haven't had beans for many years.

So, with all of that said, what does this mean for 2009? Well, for one, we will be without funding for next season. Come 12/31/2008 the USDA funding will be gone. We will not know the status of several possible options until at least 12/15/2008. We will more than likely be without a dime for 2009. I will keep you all posted through this email, and we will also keep the hotline open throughout the winter should there be a change.

The other thing about this year. Just because we have found soybean rust in a particular location, either a soybean field or kudzu patch, does NOT mean that it will be back in that location next season. Soybean rust needs to blow in from a location south of MS. So just because we are finding it in kudzu for a second year this season doesn't mean it will be back in that location next year. As a historical perspective, rust was identified in 2 counties in 2005, 9 in 2006, 26 in 2007, and 79 in 2008. I'd have to look and see which counties have had it more than once, but there have been many counties this year that have been identified for the first time. As near as we can tell rust does NOT overwinter in MS. Last season ALL of the kudzu was killed during freezes in the winter and late spring. On Tuesday we were scouting leaves in Marion County that had frost/ice on them. Hopefully we'll continue this cooler weather pattern, and kudzu will freeze early.

If you have any questions please feel free to contact me directly (662-402-9995). I will be around for most of the week, but will be on campus for the annual conference towards the end of the week. If you've never seen soybean rust, and would like to, let me know, and I can collect some leaves to bring to Starkville.

Best regards,

Tom

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Tom Allen, PhD
Assistant Extension/Research Professor
MS Delta Extension Plant Pathologist
Delta Research and Extension Center
82 Stoneville Road
P. O. Box 197
Stoneville, MS 38776
(Office) 662-686-3272
(Mobile) 662-402-9995
(Fax) 662-686-7336
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Best regards,

Tom

*****************************************
Tom Allen, PhD
Assistant Extension Professor
MS Delta Extension Plant Pathologist
Delta Research and Extension Center
82 Stoneville Road
P. O. Box 197
Stoneville, MS 38776
(Office) 662-686-3272
(Mobile) 662-402-9995
(Fax) 662-686-7336
*****************************************