Gravity tables and colour sorters have been shown to be an effective way of sorting out fusarium-damaged kernels (FDK) if the grower has the time and money to spend on the method. Gravity tables remove kernels based on density and are effective at removing heavily infected seeds, but can also result in the loss of healthy seed. Optical sorters remove kernels based on visual differences, but the process can be time-consuming and is more suited to hard wheat than soft wheat. Additionally, fusarium-damaged barley and oat do not show significant shrivelling and are not likely to be removed by equipment sorting by density, weight or colour.
It is important to remember that removing FDK (i.e. visibly infected kernels) from a grain sample does not mean that the grain is free of DON, the toxin produced by Fusarium graminearum. The relationship between FDK and DON varies and in years where infection occurs late in anthesis (or even after anthesis), visual symptoms are not always apparent whereas DON levels can still be elevated. While the Canadian Grain Commission grades wheat based on percent FDK, some markets are interested in DON levels. It is important to discuss with grain buyers and/or elevators their guidelines regarding FDK and DON. It is also recommended that growers test their grain for DON to best determine how to market it.
There is newer technology available that sorts grain based on chemical composition using near infrared transmission (NIR). This method is more effective at reducing DON levels because it is not only dependent on visual symptoms on the kernel. The machinery required to sort grain using NIR can be quite expensive to purchase, but is relatively inexpensive to run. For more information on this technology please refer to http://bomill.com/products/.
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