With corn grain harvest quickly approaching in Michigan, consider your risk of mycotoxins this year. With a wetter than normal August and September through much of Michigan, risk of mycotoxins may be high in corn this year. While prevention of mycotoxins through pre-harvest management is the best approach in reducing mycotoxin accumulation, now is the time to implement post-harvest management strategies to reduce issues at the grain elevator.
If you haven’t already, now is the time to do a late season scouting of fields to determine the amount of fungal growth and potential mycotoxins already in the field. Scouting should consist of five random spots in the field and pulling the husks off of 20 ears on consecutive plants at each location, totaling 100 ears per field. Scouting will give you a sense of which fields have high potential for mycotoxins through increased fungal activity in current weather.
Fields with higher potential for mycotoxins should be treated differently than fields with a lower potential. In general, fields that are earlier harvested will have a lower concentration of mycotoxins as fungal pathogens will have less time to develop in the ear and potentially produce mycotoxins. Also, continued damage from insects and other pests later in the season can lead to the accumulation of mycotoxins as damaged kernels allow for easier infection. Because mycotoxins can continue to accumulate during dry down, consider harvesting higher risk fields first. If there are little to no signs of fungal infections and pest damage is not a problem, allowing field drying under favorable conditions should be a safe option.
Another option to reduce mycotoxins in storage is to make adjustments to combine settings to reduce both damaged kernels and the number of kernels with fungal infections making it into storage. Physical damage to the kernels during harvest increases potential for fungal infection and for mycotoxins to develop. Adjusting the combine’s cylinder speed and clearance can reduce damage to kernels by reducing their physical contact with moving combine parts.
Also, adjustments can be made to discard moldy kernels. Increasing the fan speed so that lower density kernels are discarded can reduce the amount of mycotoxins in stored grain. Kernels infected with ear rot fungi are often lower density and therefore lighter and will be blown out. Because increasing discarded grain will decrease yield, balance this with the need to discard infected grain.
For more details, check out the research by Michigan State University.