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Getting the Facts on Fusarium Head Blight

November 2016
Updated: December 2016

Submitted by:

  • Barbara Ziesman, Provincial Specialist, Plant Disease, Saskatchewan Ministry of Agriculture
  • Holly Derksen, Field Crop Pathologist, Manitoba Agriculture
  • Michael Harding, Research Scientist, Plant Pathology, Alberta Agriculture & Forestry
Fusarium head blight (FHB) is a major disease that infects many cereal crops, including wheat and barley. The environmental conditions in 2016 were conducive for FHB across the prairies. In Saskatchewan, the 2016 survey indicates that 74 per cent of the barley, 98 per cent of the common wheat and 97 per cent of the durum field included in the survey had FHB disease symptoms. Unlike some diseases that primarily cause yield losses, FHB also negatively impacts quality due to the presence of Fusarium-damaged kernels and mycotoxins, such as deoxynivalenol (DON), that are produced by Fusarium spp.

The Saskatchewan Ministry of Agriculture has partnered with Alberta Agriculture and Forestry and Manitoba Agriculture to develop a Q & A series called “Getting the Facts on Fusarium Head Blight.” This series will address FHB issues faced in 2016 in addition to the issue that they are facing with respect to using infected seed. The answers provided will be a combined effort of the provincial disease specialists with input from researchers at Agriculture and Agri-Food Canada, the University of Saskatchewan and the University of Manitoba.

The questions and answers will be posted to the Saskatchewan Ministry of Agriculture’s blog (Sask Ag Now) as new questions and answers become available. If you have a question that you would like to see addressed in this series, please contact your provincial disease specialist.

Considerations for planting seed infected with Fusarium graminearum

The recommendations for whether or not to plant seed infected with F. graminearum vary depending on which province in which you reside. In Alberta, any grain with detectable levels of F. graminearum cannot be used for seed because F. graminearum is a declared pest under Alberta’s Agricultural Pests Act. Section 22c of the Agricultural Pests Act states: “No person shall for propagation purposes acquire, sell, distribute or use any seed, root, tuber or other vegetable material containing a pest.”

In Manitoba, there are no restrictions or thresholds for planting F. graminearum-infected seed. However, grain should be tested for germination and Fusarium infection before determining its suitability for seed.

Here in Saskatchewan, F. graminearum is not a regulated pest. However, to reduce the spread of F. graminearum into areas where it is currently not established, seed containing more than five per cent F. graminearum is not recommended for use

Deciding to use a seed treatment when sowing Fusarium-infected seed

Using good-quality seed, with high germinability and vigour and low disease incidence, is always recommended. Cleaning of grain to remove fusarium-damaged kernels (FDK) can improve grade and seed germination. In addition, seed should be planted into warm, well-drained, fertile soil at the appropriate depth. Applying fungicidal seed treatments to cereal seed is also a beneficial management practice that helps reduce risks associated with seedling mortality and reductions in stand establishment due to seed-borne, seed-transmitted and soil-borne fungal pathogens, especially when planting conditions are not optimal.

Fusarium species are examples of fungi that can cause disease on germinating seeds and seedlings and reduce plant populations. The level of Fusarium infection in a seed lot should be determined by laboratory testing, not just by counting fusarium damaged kernels. In cases where Fusarium infections reduce germination, a germination test should be used to adjust the seeding rate so that emergence and yield are not compromised. Research has shown that when seeding rates are adjusted based on germination rates, seed with low levels of infection (five to 10 per cent) have no significant improvement in emergence or yield due to a seed treatment. However, it is important to keep in mind that other soil-borne, residue-borne or seed-borne microorganisms (i.e. pests other than Fusarium spp.) can also cause diseases on germinating seeds and seedlings. Even if Fusarium is not detected on seed, a seed treatment should still be considered as a beneficial risk management tool to protect against additional threats such as Pythium spp., Rhizoctonia spp, and others.

Seed treatment recommendations for each province are as follows:

Province

Threshold

Action/Recommendation

Alberta

0%

Always use healthy seed with no detectable levels of F. graminearum. Always use a registered fungicidal treatment that includes Fusarium on the label. See the Alberta Fusarium graminearum Management Plan for more information.

Saskatchewan

2% to 3%

Use a seed treatment for F. graminearum infection in area where F. graminearum is not established

 

5%

Do not use seed when F. graminearum infection levels exceed this threshold in areas where F. graminearum is not established.

 

10%

Use a seed treatment when total Fusarium spp. infection levels exceed this threshold in areas where F. graminearum is established or when F. graminearum levels are less than five per cent in areas where F. graminearum is not established. See the Saskatchewan Ministry of Agriculture’s Fusarium head blight information page for more information.

Manitoba

None

Use clean seed with good germination. Seed treatments may improve germination. See Manitoba Agriculture’s Dealing With Fusarium Head Blight information page for more information.

Using your grain if it has high levels of DON

DON is a mycotoxin produced by the fungus that causes 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 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 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 are 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.

Recommendations:

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 the 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.

How storage of infected grain affects Fusarium spp. infection and DON levels

The viability of the Fusarium fungus during storage is dependent on the storage conditions, with temperature playing a key role. Scientific studies have demonstrated that fusarium infection levels will be reduced when infected grain is stored for at least six to nine months at a constant temperature of 25 C and where either relative humidity is greater than 62 per cent or seed moisture content is at least 10 to 14 per cent. One study demonstrated elimination of Fusarium graminearum when corn seed was stored in sealed containers at 30 C and a seed moisture content of 14 per cent. However, the same is not true for infected grain stored at cooler temperatures (less than 15 C), which are more consistent with the recommendations for grain storage on the Canadian Prairies. At temperatures below 15 C, the viability of the pathogen (Fusarium spp.) is unchanged, especially under drier conditions, making long-term storage of infected grain a poor strategy for reducing Fusarium infection levels. Also, if the grain is to be used for seed, prolonged storage of infected grain at higher temperatures and moisture levels may result in reduced vigour and germination rates.

The mycotoxin DON in Fusarium-infected grain is also unaffected by long-term storage, regardless of the temperature. Under safe storage conditions, changes in DON levels would be unlikely.  

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