Characterizing bean pod rot in Arkansas and Missouri

Green beans are an important crop grown for processing in both Arkansas and Missouri. Green beans are harvested mechanically using non-selective picking fingers. Harvested beans are then transported in bulk to processing plants that are located at various locations throughout the midSouth. Thus, the crop is managed for high quality, avoiding pod blemishes caused by insects and diseases. One of the consistent quality problems that affect Arkansas and Missouri green bean crops is pod rot. Two of the causal agents of pod rot that have been reported by researchers and vegetable companies alike are Pythium aphanidermatum and an unidentified Phytophthora sp. In this study, 15 growers’ fields were selected and soil samples (at planting), pod samples (at harvest), and environmental data were taken from each field. Disease incidence for field sites ranged from 0 to 7.3%. Pathogens associated with pod rot were Sclerotinia sclerotiorum, Rhizoctonia solani, a Phytophthora sp., and Pythium spp. The two suspected causal agents for pod rot, Pythium and Phytophthora spp., were found in all but one of the 12 field sites assessed for pod rot. Pythium inoculum potential, as determined by a baiting technique, was not a good indicator of pod rot incidence. In addition, soil temperature and water were not associated with pod rot. Pods collected at harvest having symptoms of pod rot were either in direct contact with the soil, senescing leaf tissue, or other diseased pods