Southern Rust Confirmed North
Southern rust has been confirmed in several counties across our footprint. The disease has migrated north earlier than usual and is alarming because of the number of late planted corn acres. Early detection of foliar diseases and properly timed fungicide applications can stop disease development and be economically beneficial.
Southern rust of corn
Southern rust has small, densely clustered, round to oval, light orange colored pustules and are found on upper leaf surface, husks and leaf sheaths. Optimum conditions for rust development are temperatures from 80 to 90 degrees F and high humidity. Fungicide applications may be warranted if 3-5 percent of the leaf surface has rust pustules, corn is four or more weeks from black layer, and high humidity and rainfall are in the forecast. Fungicide application is preventative and should be applied in time to protect non-infected areas on the corn plant.
The map below from http://ext.ipipe.org/ shows the confirmed progress of southern rust as of July 28.
Other foliar diseases
We have seen septoria brown spot and frogeye leaf spot in soybeans fields across the region. Septoria brown spot symptoms are brown to black spots found in the lower canopy first but will most likely move up due to the wet, warm weather. Frogeye leaf spot can be recognized by angular spots with light gray centers and distinct purple to red-brown margins. We have not seen white mold in soybeans to date, but next week’s forecast favors white mold development. We are still seeing gray leaf spot in corn; this disease starts out as small pinpoint lesions surrounded by yellow halos which develop into long rectangular lesions as the disease progresses on susceptible hybrids.
Contact us with any questions you have about foliar diseases,
Terry, Dan, Rod and Dennis