There are numerous seed borne and soil borne pathogens that can infect and cause disease on germinating seedling and roots of soybean. The environment has a very large impact if the pathogens have suitable conditions to grow and infect plants. Saturated soils will favor the watermolds, Phytophthora sojae, Phytophthora sansomeana, as well as the many, many Pythium spp. and the fungus Fusarium virguliforme which causes sudden death syndrome. Dry soils will favor other fungi like Macrophomina phaseolina, which causes charcoal rot. Pathogens like Fusarium graminearum and Rhizoctonia solani can infect across all levels of moisture. Temperature can also play a role in the development of these diseases. Cool soils will favor some of the Pythium spp., while warmer soil conditions will favor Phytophthora sojae and Pythium aphanidermatum.
One of the most important contributing factors to the development of disease is the resistance level in the host. Most cultivars sold in Ohio have good levels of resistance to both Phytophthora sojae (Figure 1) and soybean cyst nematode (Figure 2). These two are critical for many regions in Ohio.
Figure 1. Early season damping-off caused by Phytophthora sojae
Figure 2. Very small white cysts of females and larger white Rhizobium nodules
Find more information on these diseases by clicking on the disease name below:
Phytophthora Seedling Damping-Off and Root Rot
Rhizoctonia Seedling Damping-Off and Root Rot