03 Jul Fusarium Head Blight: What You Should Know
Fusarium Head blight (FHB) is a fungal infection caused by species in the Fusarium genus of fungi and has been one of the most economically costly diseases in cereal production in North America since the 1990s. Between 1993 and 2001, FHB caused an estimated loss of $2 billion USD in the USA and an estimated loss of $520 million CAD in Canada (1). Hot, humid conditions just prior to flowering (as we are seeing this year in Manitoba) are the ideal conditions for Fusarium to develop, so what should you know about FHB?
The species Fusarium graminearum is the most common culprit of this infection and causes disease in cereals such as wheat, barley and corn (where it is most often referred to as Fusarium Ear Blight). This fungus appears in early summer as flowering begins, and infects the heads of cereal crops (2). Fusarium infects grain kernels, causing a milky white or pink discoloration and causing them to shrivel up and lose mass. The fungi later reach a reproductive spore-bearing stage, resulting in black lesions on kernels. This results in a lower quality crop in general and lower yields to reduced test weights. Fusarium infection also causes sterility in the flowering stage, further hampering yield potential (2).
The principal concern with Fusarium infection besides yield loss is the production of mycotoxins. Fusarium species sometimes produce mycotoxins as a secondary metabolite. The most important of these mycotoxins is called Deoxynivalenol (DON), which is released onto plant heads during Fusarium infections (3). Mycotoxins like DON can have serious health effects in both humans and animals, so this problem affects grain for both human consumption and the animal feed market. Presence of DON in your final yield will decrease its value on the market and may even make your crop unsellable if it is present in high enough concentrations.
Here are some tips to keep your wheat at its best when dealing with Fusarium:
- Currently there are no commercial cultivars totally immune to FHB, but resistant varieties are being bred for resistance genes and some cultivars are commercially available, e.g., AAC Cameron VB and CDC Credence.
- Removal of lighter, infected grain kernels at harvest can keep your yields at a higher quantity and quality. Adjusting your combine to remove lighter weight kernels along with chaff is an option. Using gravity table grain separation is an effective option for removing FHB infected kernels from harvested wheat.
- Commercial seed treatments and fungicides exist that can help keep Fusarium at bay. Triazole-containing fungicides have been shown to be the most effective at limiting both FHB and DON, and should be applied at early flowering e.g. Caramba® and Fungi-Phite® Cereals.
- One of the most common routes of infection is the re-distribution of Fusarium present in the residues and chaffs from previous crops. Fusarium survives best on larger crop residues that are left above ground to slowly decompose, so tilling soil to break up and bury crop residues can reduce the potential for infection.
- There is ongoing research into biocontrol technologies for use against Fusarium, such as PGPR (Plant Growth Promoting Rhizobacteria), to control this pathogenic fungus. Hopefully a biological product to combat FHB will be available in the near future.
At the end of the day, no one method of prevention is guaranteed to be effective, so a combination approach of preventative measures as well as diligent crop monitoring are the best way to curb your Fusarium problems.
1) Xia, R., Schaafsma, A.W., Wu, F., Hooker, D.C. (2020). Impact of the improvements in Fusarium head blight and agronomic management on economics of winter wheat. World Mycotoxin Journal, 13 (3). https://doi.org/10.3920/WMJ2019.2518
3) Wachowska, U., Kucharska, L., Jedryczka, M., Lobik, N. (2012). Microorganisms as Biological Control Agents against Fusarium Pathogens in Winter Wheat. Pol. J. Environ. Stud., 22(2).