[Grainssoybeans] Soybean Rust Update
From: Curtis D. Fountain
Agricultural Extension Agent – Field Crops
Please read the below message from Dr. Jim Dunphy and Dr. Steve Koenning.
A strobilurin fungicide or a triazole fungicide or a combination fungicide (combination of strobilurin & triazole) is recommended. As noted below, the 2013 NC Agricultural Chemicals Manual (Page 420) provides additional information. Also attached isManagement of Soybean Diseases Fungicide Efficacy for Control of Foliar Soybean Diseases – April 2013.
Thorough spray coverage is important. In general, high spray pressure, high water volume, and nozzles producing fine-to-medium-sized droplets are needed to penetrate the canopy. In general, spray volumes of at least 15 gallons/acre are recommended. Read the fungicide label for minimum spray volumes/pressures. According to the TeeJet (there are other brands) website, recommended spray nozzles include turbo Twinjet twin flat spray tip, XR Teejet extended range flat spray tip, XRC Teejet extended range flat spray tip, Twinjet twin flat spray tip, and turbo Teejet duo dual polymer flat fan spray tip.
Rust will typically take 10-20 days from initial infection to develop to detectable levels. It will take another 7-14 days to spread to other leaves on the same plant, and another 10 days to cause significant defoliation. This assumes optimal conditions for rust (65-85 degrees F & either overcast skies or rainfall) through much of the period.
September 19, 2013
from Jim Dunphy, Extension Soybean Specialist, and
Steve Koenning, Extension Plant Pathologist,
Asiatic Soybean Rust was confirmed earlier today on a soybean sample from Cumberland County, NC. Combined with the confirmed finds in Scotland and Cleveland counties, NC, and Suffolk County, VA, essentially all the state’s soybeans are within 100 miles of known rust. Samples received this week from Catawba, Columbus, Gaston, Granville, Hoke, Lincoln, Pasquotank, Robeson, Rutherford, and Wayne counties were all negative for rust.
We would consider that rust spores may well be in any soybean field in the state, but as dry as it is in much of the state, we wouldn’t expect the disease to develop very rapidly. We would recommend spraying a fungicide on any soybeans in the state which have started blooming, which do not yet have full sized seeds in the top four nodes of the plant, and which appear to have a yield potential of 20 Bu/A or more.
Rust has now been confirmed this year on soybeans in 110 counties or parishes in ten states (LA, FL, AL, MS, GA, NC, SC, AR, TN, & VA).
Some sources for more detailed information on Asiatic soybean rust are listed below: soybeanfungicides(4)
The USDA soybean rust web site http://www.sbrusa.net/
The North Carolina Agricultural Chemical Manual http://ipm.ncsu.edu/agchem/