If you've ever started seeds, you've undoubtedly experienced having seedlings suddenly keel over at the soil line. This condition, called damping off, is typically caused by two different fungi: Pythium and Rhizoctonia. Researchers with Agri Food Canada have found that fish emulsion can be an effective preventative.
Canadian researchers grew cucumber and radish seedlings in a peat-based, potting soil mix. One group was treated with a 4 percent fish emulsion solution. Another group received the equivalent dosage in inorganic fertilizer. Both groups were inoculated with disease spores and left to incubate 1, 7, 14, and 28 days in plastic bags. Cucumber and radish seeds were then sown in the bags for each treatment. The bags that were incubated with fish emulsion for 7 days or longer had a 70 to 80 percent protection rate from damping off disease. No disease control was found in the bags treated with inorganic fertilizer.
This research suggests fish emulsion is not only a good plant food for young seedlings because of its highly soluble form of nitrogen, but it also helps create an environment that suppresses damping off disease.
For more on this research, go to the Canadian Journal of Pathology Web site at: pubs.nrc-cnrc.gc.ca/tcjpp/k04-012.html