Source:  Steve Koenning & Jim Dunphy,  NCSU COOPERATIVE EXTENSION, 8/24/11

North Carolina State University and Cooperative Extension
Steve Koenning Extension, Soybean Pathology Specialist, and
Jim Dunphy, Soybean Specialist, Crop Science

       Hurricane Irene seems likely to impact North Carolina this weekend.  If Hurricane Irene makes landfall or draws air and moisture across Florida before it arrives in North Carolina, it may pick up soybean rust spores and could deposit them in North Carolina this weekend.  Still the likelihood of a late season epidemic of soybean rust seems remote.  If spores are deposited on soybean this weekend, it would probably be four weeks before we detected soybean rust, and yield loss at this point would not be measureable.  Affected fields would require an additional two to three weeks before disease loss would be perceptible and this puts us at mid-October, when the majority of our soybean crop is mature.  

       Late planted soybean would obviously be more likely to benefit from a fungicide, and have greater potential for developing soybean rust at damaging levels. As dry as most of the state is, many fields would be accessible with ground equipment by late next week if the need to spray arises. The general level of soybean diseases may become worse following the Hurricane, so soybean may benefit from a fungicide application to protect quality and quantity of the soybean crop at this time.  

       Thus far in 2011, soybean rust has been detected on kudzu in New Iberia parish in Louisiana, several locations in Florida, and presumably is active in Mexico.  The potential for spread from these regions at this time is unlikely. Very hot weather throughout most of the Southeast remains as a major impediment to development of rust at this time. We are starting to receive samples from sentinel plots, and foliar diseases are less frequently encountered this year than any year in the recent past.

SENTINEL PLOTS IN NORTH CAROLINA

       Sentinel plots are in place in about 23 locations in North Carolina, and we will continue to monitor them for soybean rust until frost.  This effort is supported through soybean check-off dollars.

       We reserve the right to recommend fungicide applications to researchers and some few others, such as seedsmen, that may not be applicable to the majority of soybean growers.  Research plots in particular can be ruined or the information devalued if disease is not uniform throughout an experiment.  Thus, the value of research and or seed increase plots may exceed thousands of dollars per acre.


PROSPECTS FOR SOYBEAN RUST IN NORTH CAROLINA IN 2011

       The northward progression of soybean rust appears to be stalled this summer in Florida.  Watch for tropical storm events that bring moisture from the south.  We learned last year that rust can and will make large jumps distance wise over a relatively short period of time.  Additionally, the national forecast is for an above average tropical storm season.  Tropical storms, especially those moving through Florida and Georgia, may provide for transport of rust spores earlier in the season.


Resources for Soybean Rust in 2011:

The North Carolina Agricultural Chemical Manual

http://ipm.ncsu.edu/agchem/agchem.html

The IPM PIPE web site

http://sbr.ipmpipe.org/cgi-bin/sbr/public.cgi

Soybean Rust in the Mid-Atlantic Region

http://cipm.ncsu.edu/ent/SSDW/RustBulletin08.pdf



Soybean Disease Update for August 2011

       Very few disease problems have been detected on soybean in North Carolina in 2011.  Foliar diseases in particular have been rare.  Some soil borne diseases, such as Pythium, Rhizoctonia, and Phythophthora, have caused problems, but these have been limited in extent and often related to poor conditions at planting.  Southern soybean stem canker was identified in the Piedmont, which is a rare occurrence for the Carolinas and Virginia areas.

       By far the most common problem associated with dead or dying plants in 2011 is the lesser corn stalk borer.  Although we encounter this problem every year, 2011 has seen record numbers of this pest on soybean come through the Plant Disease and Insect Clinic.  The good news is that lesser corn stalk borer is a relatively rare occurrence.  The bad news is that we can expect to continue to lose soybean plants from lesser corn stalk borer and that it is difficult to control under the best of conditions.

       Foliar fungicides, though labeled for use on soybean, are not generally recommended for North Carolina for disease control. Soybean grown for seed may show some improvement in seed quality, especially with applications at the R5 growth stage.  Still, a timely harvest is the best insurance for good seed quality.