Taproot decline (TRD) was detected in a soybean field near Belforest in Baldwin County this week. The disease, first detected in Alabama in 2016, has now been found in 21 counties across the state. The first reports of TRD in the United States were from Arkansas, Louisiana and Mississippi in 2007. However the pathogen was not formally identified until 2017 (https://www.plantmanagementnetwork.org/pub/php/volume18/number1/PHP-01-17-0004-RS.pdf). Taproot decline is caused by a previously undescribed species in a genera of wood-rotting fungi commonly seen in forests called "dead man's fingers" (Xylaria arbuscula). Foliar symptoms of TRD may be easily confused with other soil-borne diseases such as Sudden death syndrome (SDS), charcoal rot and southern blight. TRD infected plants exhibit interveinal chlorosis in the middle canopy prior to bloom, and foliar yellowing in the upper canopy at full pod. Infected plants have blackened roots which often break off below the soil line when pulled from the ground.
Symptoms of TRD include foliar yellowing and blackened taproot.
Taproot decline has a wide distribution throughout the southern soybean production area and is increasing in importance. Little is known about the causal organism or the disease. We are currently working with Mississippi State, Louisiana State University and University of Arkansas to survey for the pathogen and determine best management practices for TRD. Research on TRD is currently focused on identifying varietal resistance to TRD in soybean, determining fungicide effectiveness, crop rotation & tillage options, identifying alternative hosts for the pathogen, and estimating yield loss to the disease. If you suspect you have TRD in your field, please send whole plant samples to the Auburn University Plant Diagnostic Lab with the following information: field location, variety, plant-growth stage and field history. This will help us better understand the distribution of TRD within Alabama.
Edward Sikora and Kassie Conner
Alabama Cooperative Extension System
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