Diaporthe phaseolorum var. sojae and Phomopsis species
Pod and stem blight is a fairly common and widespread disease of soybeans in NY, considered to be of low economic importance. The disease is favored by prolonged periods of warm, wet weather during pod fill and maturation. Infection occurs at any stage of development, but symptoms usually appear on senescing tissues, including stems, petioles and pods as numerous black dots. The black dots are the pycnidia (fruiting body) of the fungus, and may be arranged linearly, sporadically, or concentrated near the nodes. The pathogen survives on soy debris or in seeds, and spores are splashed from debris onto successive crops. Because it is considered a disease of low economic importance, foliar fungicide applications are not likely to be cost effective, unless in a seed production field. Genetic resistance is not widely available in soybean varieties. Tillage practices to bury infected residues and rotation with non-host crops, including small grains or corn, are recommended for highly infested fields.
- Soybean Stem Diseases: What are the Different Symptoms and Signs? - Penn State University key for identifying soybean diseases
- New York State Disease Survey - locations of diseases found as part of a disease survey sorted by disease and by county.