farmgate: Why Has So Little Been Said About Soybean Rust This Year?
Here’s a question for you. Why is it you have heard very little about Asian soybean rust this year? Knock on wood; we don’t want to hear much about it, but with all the rain in the Cornbelt, that was supposed to be the precursor to our soybean crop being ravaged by rust. Are we missing something?
Asian soybean rust has been a threat for the last five seasons since a few spores blew ashore with hurricane force. Soybean pathologists were prepared and the sentinel system was created along with lines of communication to keep everyone informed. Although rust has been found in many Cornbelt states, its arrival apparently has been too late to do any damage. Experts said wait for a year that is unusually wet, and we have certainly had that this year.
Your first point of consultation should be the official Asian soybean rust website. It will provide an update when necessary about the latest findings, which shows active rust areas in Texas, Alabama, Florida, Georgia, Louisiana, and Mississippi. So soybean rust is alive and well, but apparently thriving in the south where it usually remains during the major part of the growing season.
But therein lies the rub. The Cornbelt growing season has been modified this year with delays from spring coolness and early summer excessive rains. Soybean maturity is behind last year and all of the years since soybean rust arrived in the US. Monday’s USDA crop progress report indicated 78% of the soybeans in the 18 major production states were blooming, compared to 90% last year and 88% for the five year average. Also, only 37% of the soybeans were setting pods, compared to 64% last year and 58% for the five year average.
With the soybean crop behind typical development, will that mean a greater potential for damage from soybean rust this year when it makes it typical late season dash toward the Cornbelt? There is no answer for that, however, Iowa State plant pathologist Daren Mueller says rust is moving northward much slower than it has for the past several years. Asian rust needs moisture to survive, and while the Cornbelt has had plenty of that, the opposite has been the case in the Gulf Coast states where rust has been restricted in its movement. Mueller points to the latest Drought Monitor map which shows the Gulf Coast in either moderate drought or abnormally dry. However the latest map pre-dated Hurricane Dolly and Tropical Storm Edouard which brought rain to Central Texas where some of the driest areas are located.
Mueller’s latest analysis indicates the chance of Asian rust moving into the Cornbelt soon appears to be low. He says late planted soybeans in Iowa are on track to reach the full seed stage in mid-September, and currently he is not overly concerned.
Anne Dorrance at Ohio State isn’t that concerned either. She and her colleagues remind farmers in their current newsletter that no soybean rust pustules have been found in the Midwest. They are monitoring traps that have collected spores for the past three years. The Ohio State researchers say the spores that have arrived in the past have been either killed by drying out in the atmosphere while enroute or succumbed to ultraviolet light rays. They acknowledge all of the rain this year in June and July, but say the past several weeks the drier weather pattern has not been conducive to any rust spores that might have arrived.
The Ohio State specialists say they are not recommending any fungicide applications be made at this time to manage soybean rust. They say early soybeans are “out of the woods,” at this point, but later planted beans still are at risk of rust damage.
Summary:
Despite wet Cornbelt weather, Asian soybean rust has been a non-factor this year, but there is still quite a bit of time required by soybeans to reach the point of maturity when rust will not be able to damage yields. Dry weather has prevented its movement out of the Gulf Coast states, but soybean producers with late planted soybeans should monitor authoritative sources for any alerts to implement their fungicide action plan.
Posted by Stu Ellis on August 7, 2008 12:28 AM to farmgate