Areas of Ohio were beginning to show abnormally dry conditions in mid-June. Areas of southern Ohio entered extreme drought conditions (D3) in August and exceptional drought (D4) by the first week of September. Due to dry conditions, soybean pods showed a weakened structure in early to mid-September (Figure 1).
Due to drought conditions, soybeans matured and dried down in the field extremely quickly, making timely harvest very challenging. Some farmers postponed harvest due to tough stems or the plants retaining leaves. Other farmers with extremely dry seed (6 to 8 percent moisture) may have delayed harvest in hopes of harvesting at a higher moisture after Hurricane Helene’s rainfall.
From September 26 through September 30, rainfall totaled between 2 to 8 inches in western, central, and southern Ohio with average air temperatures in the mid to high 60s. After dry seed was exposed to these weather conditions, there were multiple reports of sprouting (Figure 2). So far, soybean sprouting issues have been reported in several Ohio counties: Clark, Madison, Fayette, Fairfield, Pickaway, Ross, and Miami.
Rainfall during soybean harvest is a common occurrence in Ohio. However, compromised pod integrity led to the soybean seeds germinating and sprouting within pods after Helene’s rainfall. Rapid maturation of seeds due to the drought may have also led to issues with properly progressing through the final stage of seed development of maturation/drying. Seeds normally go through the final stage of maturation where seed coats will slowly contract and harden as seeds gradually lose moisture while they decrease their metabolism to enter into a state suitable for storage (aka quiescence). If maturation and drydown occur prematurely or too rapidly, as could occur due to drought conditions, the seed coat integrity may end up being compromised. Seed coats help to protect seeds from physical damage, but also work to control water uptake. An abnormal seed coat could have been contributing to the increased germination on plants we have seen this fall as 
compared to past years due to an inability to restrict water uptake by the seed embryo. Disruption of hormonal controls within the seed under drought during maturation may also be contributing to this season’s precocious germination (i.e. germination while attached to maternal plant; vivipary). In general, abscisic acid (ABA) hormone works to prevent seed germination whereas gibberellic acid (GA) will cause seeds to germinate. If non-deep physiological dormancy controls aren’t put in place during seed maturation by ABA, it could lead to an increase in premature soybean germination. It’s also possible that GA pathways within the seeds were stimulated by recent rains and induced seed germination.
We are also receiving reports of soybean plants with black pods and stems. We hypothesize that one or more fungi are responsible for the observed intense black discoloration of the pods. The severe and prolonged drought conditions, which accelerated soybean maturation, also created an environment conducive to the activation of saprophytic fungi. Subsequent rainfall facilitated the rapid growth of these fungi, resulting in the intense black discoloration of the pods. Moreover, fungal species within the Diaporthe/Phomopsis complex, associated with seed decay, were more prevalent in these plants. Alternating periods of dry and wet weather contributed to pod deterioration and splitting, which in turn increased the susceptibility of mature seeds to fungal infection. Further characterization of these fungi is currently underway.
If you have plants exhibiting these symptoms, please send samples to Dr. Horacio Lopez-Nicora at:
OSU Soybean Pathology and Nematology Lab
Attn: Horacio Lopez-Nicora Ph.D.
110 Kottman Hall
2021 Coffey Rd.
Columbus, Ohio 43210
lopez-nicora.1@osu.edu