As the earliest planted soybeans in Tennessee near reproductive growth stages, scouting for disease is critical to determine how necessary a fungicide application may be in protecting yield from disease.

The amount and severity of a disease and effect on yield are closely associated with environmental conditions, management practices, growth stage and susceptibility of the soybean variety planted.

Some diseases have characteristic symptoms that are easily identified, where others may not be specific and may be mistaken for weather or chemical damage. Entire plant samples should be examined and when needed can be taken to your local Extension county agent for identification.

Some common soybean diseases found in Tennessee include frogeye leaf spot, septoria brown spot, cercospora blight, anthracnose, southern stem canker, charcoal rot, and sudden death syndrome.

Descriptions of symptoms, pictures, and management options for these and other soybean diseases can be found at UTCrops.com (Soybean Disease and Nematode Identification Field Guide).

Many diseases can be avoided by planting a disease resistant variety, regularly rotating to non-host crops, and when warranted fungicide applications can be applied. 

UT research has previously indicated that under circumstances of high disease pressure and conducive environmental conditions, timing a fungicide application at R3-R5 (beginning pod develop to beginning seed development) often provides the most consistent yield protection.

A foliar fungicide efficacy table (Soybean Fungicide Efficacy Table) found at UTCrops.com) was developed by The North Central Regional Committee on Soybean Diseases and the Regional Committee for Soybean Rust Pathology (NCERA-212 and NCERA-208) to provide information on foliar fungicide efficacy for control of major foliar soybean diseases in the U.S.

With the identification of frogeye leaf spot disease caused by strains of Cercospora sojina resistant to fungicides in the quinone outside inhibitor (QoI or commonly referred to as strobilurin) group in Tennessee since 2010, it is recommended to use a fungicide that has a mixed mode of action or one that is not a sole QoI/Strobilurin product.