Since September, I have received questions about the seedborne spread of white mold by infected soybean seeds. More questions followed after the publication of my article Check the Soybean Seeds in the October 13, 1997, ICM Newsletter. Two general types of questions were commonly asked:
- If the pathogen can infect soybean seeds, can the infected seeds disseminate white mold fungus into a new crop of soybean? We know that seeds mixed with sclerotia are very effective in disseminating the disease, which has been evident by many cases of bin-run seeds. Plant pathologists are working on whether or not infection of the seed itself can play a role in spreading the disease. We know that these infected seeds are of poor quality--they are whitish, shriveled, usually small in size, and germinate very poorly. If you want to save seed from a white mold-infested field, seed testing at the ISU Seed Science Center is highly recommended. Their phone number is 515-294-6821.
- My soybean field had a white mold problem this year. I think the fungus was from seeds used this spring because I saw mold on the seed coat. Am I right? This rationale is incorrect. If infected seeds indeed disseminate the white mold pathogen into a field, it would take a few years for the disease to build up to a level that one can detect with an untrained eye. Furthermore, other fungi can cause mold-like symptoms on seed coats. The white mold pathogen also can be disseminated by many other means such as wind, infested manure, and combines. See the fact sheet Soybean White Mold (Pm-1731) for details.
This article originally appeared on page 188 of the IC-478(24) -- November 17, 1997 issue.