Deoxynivalenol (DON) is a mycotoxin produced by the fungus that causes fusarium head blight (FHB). The importance of determining DON levels in your harvested grain relates to the use of that product for human/animal consumption. DON is poisonous to humans so it is carefully monitored in grain used for food. Additionally, it is poisonous to livestock and can cause feed refusal and poor weight gain in livestock if present above recommended levels.
The relationships between fusarium-damaged kernels (FDK), seed infection by Fusarium spp., and DON levels are not consistent. Just because FHB was observed in the field and/or FDK were observed in a harvested sample it does not necessarily mean that DON is present. Conversely, the lack of these symptoms does not necessarily mean that DON is not present. The latter situation is often the case in years where conditions are conducive for Fusarium infection after anthesis. These DON levels are not accounted for when grading grain is based solely on the percentage of FDK.
While DON levels may affect the suitability of harvested grain as food or feed, seedling health and seed germination is affected by the extent of infection of seed by hyphae of Fusarium graminearum. Thus, the level of infection by Fusarium spp., including F. graminearum, is a better measure of whether or not the grain should be used for seed in a subsequent season.
For purposes of replanting, growers should have seed tested by an accredited lab for germination, vigour, and Fusarium infection levels. Based on this information growers can determine whether or not a grain sample is appropriate for planting (with or without a seed treatment) and whether the seeding rate would need to be adjusted. (See future questions in this series that will address whether or not to plant Fusarium-infected seed.)
For purposes of marketing and livestock feeding, growers should have grain tested for DON levels by an accredited lab. Grain companies and buyers are increasingly requesting information on DON levels as opposed to just FDK.
Holly Derksen, Field Crop Pathologist, Manitoba Agriculture
Barbara Ziesman, Provincial Specialist, Plant Disease, Saskatchewan Ministry of Agriculture
Michael Harding, Research Scientist, Plant Pathology, Alberta Agriculture & Forestry