First Report of Phomopsis longicolla Causing Stem Necrosis on Soybean in Arkansas

Abstract

Soybean plants (Glycine max (L.) Merr.) with stem necrosis symptoms were observed in several fields across southeast Arkansas, USA in 2016. Symptoms included reddish-brown elliptical lesions that progressed to slightly sunken cankers of varied lengths on stems with pycnidia sometimes observed in the area of necrotic tissue (Mathew et al. 2015; Vidic et al. 2013). Cankers girdling the stems 5-8 cm above the soil line were often found. Severely impacted plants were aggregated in approximately 3-10 m patches with a disease incidence >95% and <10% incidence more widespread in fields. In severely affected areas, symptoms advanced up the plant with necrosis occurring at petiole bases resulting in leaf and petiole pruning and pod abortions. Approximately 50 symptomatic plants were sampled from 5 fields in Desha (33.797790°, -91.278337°; 33.809550°, -91.278975°; and 33.946060°, -91.412891°), Lincoln (33.950424°, -91.902375°), and Jefferson (34.193164°, -91.902375°) counties. Forty fungal isolations from 3 cm piec...