Managing Fusarium Head Blight At Harvest

Unfortunately at a late stage in the growing season when harvest is right around the corner, there are no easy answers in managing fusarium head blight (FHB) that is present. However, before harvest (and before a preharvest treatment is applied if one is planned), farmers and agronomists should head out to the fields for some final scouting to determine what, if any, harvest and storage strategies can be used to minimize the impact of fusarium damaged kernels. Careful harvesting, drying and storage strategies are the farmer’s best way to try and maximize grain quality and marketability.

Harvest

The key at harvest is to try and prevent infected kernels from going into storage. Here are a few suggestions:

Thoroughly scout each field noting if there are any differences in infection levels between fields or if there are patterns within fields that are more affected by FHB, such as low areas or fungicide application misses. If possible, harvest those fields and/or areas separately.
Use higher fan speeds to try and blow infected kernels out the back, if the rest of the grain is of good quality. Many times the infected kernels are smaller, lighter and more shrunken than healthy kernels. Research at Ridgetown found there was a tenfold decrease in Fusarium-damaged kernels in the grain sample when fan speeds were operated to deliver maximum air blast. However, the downside to this strategy is higher fan speeds can result in healthy kernels going out the back as well. In the study at Ridgetown, up to 2 bushels per acre of healthy kernels were also lost. Farmers must weigh yield loss and marketability of the harvested product. The other downside is that higher fan speeds will likely not remove all the damaged kernels because if FHB infections occurred late in the development of the kernel, those infected kernels still may be fairly plump and chances are will be retained in the sample.
Reducing combine travel speed may reduce Fusarium-damaged kernel levels. The slower combining speed allows for increased separation of the grain by allowing the increased air blast time to separate the good kernels from the infected kernels.
Harvest early if possible at slightly higher than normal moisture contents. However, do not harvest above 18% M.C. as higher moisture grain reduces the ability to blow the lighter damaged kernels.
After harvest, gravity table grain separation may be effective in removing light-weight, damaged kernels. The increased marketability of the cleaned grain may pay for the cost of the clean-out process.

Drying

Dry infected grain to a storage moisture content of at least 14% in a heated air dryer to stop further disease development. To maintain milling quality, do not allow the temperature of the grain to reach 60°C (140°F) for any significant length of time.

Storage

As mentioned earlier, not only can Fusarium levels vary between fields but also within the field. If there are differences and harvested accordingly, bin harvested grain separately. Fusarium damaged crops must be stored properly to prevent further mould and toxin development.

Seed And Feed Considerations

It is always recommended to plant seed of high quality. Studies have shown that fusarium-damaged kernels have affected stand establishment and yield; therefore it is important to not use seed with high levels of Fusarium. If considering using fusarium damaged seed, it should be cleaned and conditioned to try and remove the majority of damaged kernels. Commercial seed laboratories can test to determine the percentage and species of Fusarium. A germination test should also be done.

Seed treatments will limit seedling blights caused by seed and soil-borne pathogens, including Fusarium species. However, seed treatments will not prevent FHB from developing later in the season from stubble-borne inoculum where Fusarium species are already present.

Fusarium infected grain may contain mycotoxins, the most common being deoxynivalenol or DON (vomitoxin). However, the presence of Fusarium-damaged kernels does not automatically mean mycotoxins are present. The occurrence, amount and kind of mycotoxins may depend on several factors, including environment, species of fungus present, severity of infection and the variety or kind of crop. If there are plans to use the grain as feed, get it tested prior to feeding. For more information on feeds and feeding considerations, check out the following Manitoba Agriculture website: http://www.gov.mb.ca/agriculture/livestock/production/beef.

Sources:

“Harvest and Storage Strategies to Minimize Fusarium 2010” by Helmut Spieser, Environmental Engineer, OMAFRA Ridgetown. June 2010.
“Fusarium Head Blight (Scab) of Small Grains” by Marcia McMullen - Extension Cereal Pathologist, Shaobin Zhong - Wheat Pathologist & Stephen Neate - Barley Pathologist; Department of Plant Pathology, North Dakota State University; September 2008.
“Fusarium Head Blight” by Saskatchewan Agriculture and Food, August 2007.