There are reports across the state of concerns about soybean seed quality, primarily discolored and moldy seeds, as harvest progresses. Ann Dorrance, OSU Extension Soybean pathologist has been out on numerous fields investigating the issue and her lab has received many samples. In the latest OSU Extension CORN newsletter, Anne has summarized some of the fungal organisms responsible for the seed damage, along with a description of the symptoms. That entire article, with explanatory photos, is available on-line at https://agcrops.osu.edu/newsletter/corn-newsletter/2018-34/full. The bottom line is that all of these fungi can affect seed health, can detrimentally affect marketing, and can potentially affect the 2019 crop. Here are Anne’s management recommendations as a result:
“Fields that have a high incidence should not be used for seed, but should be fine for feed but best in low quantity. To my knowledge, there are no animal toxins associated with these fungi like we see for head scab. For fields with low incidence, many seeds will be asymptomatic so when a fall germination test is done, the percentage of moldy seed maybe high. Some of the seed may have some mycelium on the outside layers but have not reached the young soybean. Over the winter, under dry conditions, the mycelium (fungus) on these outside seed tissues will die and then those seed will appear normal in a germination test. The point here is to keep the seed dry to prevent any further colonization of the seed.
These fungi ALL overwinter on crop residue which then serve as inoculum for the 2019 soybean crop. This is especially important for the no-till continuous soybean fields. There are a few management strategies that can be done for 2019.
a) Don’t plant the same variety back in the same field – Rotate varieties and look for those with better resistance scores than your current one.
b) Do something to help break down the residue, it doesn’t need to be a lot, but some light tillage to bury some of the residue will go a long way.
c) Rotate to wheat, barley, or corn. These are non-hosts for this group of pathogens and planting something else in that field will go a long way to reducing inoculum for when soybeans are put back in that field.