Fusarium head blight’s potential to devastate barley alarms scientists and farmers alike. To limit disease transference, growers who have cereal crops near infected fields must be extremely vigilant, whereas growers outside of currently affected areas should test and avoid planting infected seed.
FHB, also called scab or tombstone, is caused by several species of the Fusarium fungus, the most significant being F. graminearum (Fg). Farmers in Manitoba, eastern Saskatchewan, and irrigated areas of southern Alberta battle Fg every year.
Fg fungi overwinter in the soil, surviving on infected cereal and corn residue and on seed. Fg spores emerge in the spring and summer, causing Fg spread to cereal and grass heads at the flowering stage. Spores that reach a cereal flower can infect the developing kernel. Infected heads may exhibit white or pinkish fungal growth that produces more infective spores. Spores are carried on air currents to other plants and adjacent fields. Like most fungal diseases, Fg thrives in moist weather and rising summer temperatures, but it doesn’t need much moisture—a shower is enough to spread the disease and create conditions that favour head infection. Soil-borne Fusarium inoculum can infect plants at different stages of growth, causing seedling blight and crown and root rot in cereals, as well as stalk and ear rot in corn.
FHB reduces yields of barley and other cereals. However, mycotoxins produced by Fg species in affected grain are of greatest concern. Fg typically produces more mycotoxin than the other Fusarium species. The main toxin is deoxynivalenol (DON) and grain buyers specify a maximum permissible level of DON for their purchases. Agriculture and Agri-Food Canada advises a maximum of 1 ppm of DON for swine, dairy cattle, and horses, and 5 ppm for poultry, beef cattle, and sheep. Maltsters have zero tolerance for DON—it leads to beer that gushes when opened.
Because FHB is so destructive and easily spread, Alberta designated Fg as a “declared pest” under the Agricultural Pests Act in 1999 and has developed a set of best management practices to control it. These practices are described in the Alberta Fusarium graminearum Management Plan.
Where Fg is not established
- Plant disease free seed
Where Fg is established (primary management strategy)
- Plant seed with low detectible Fg
- Rotate crops from cereals to non-host crops (two years away from small cereal grains and three years or more away for corn); use pulses, canola, or forage legumes for at least two consecutive years in crop rotation
- Use ‘least susceptible’ varieties
- Limit Fg seedling blight by treating seed with a fungicide
- Apply a timely foliar fungicide (early flowering stage) to prevent stubble borne Fg infection
- Limit irrigation during flowering period
- Learn the disease symptoms
Other management strategies
- Increased seeding rates reduce tillering and therefore shorten a field’s overall flowering period, which decreases infection time susceptibility and improves fungicide performance.
- Stagger planting dates to avoid having all cereal fields flowering simultaneously
- Effectively chop and spread straw and chaff during harvest
- Residue burial via tillage may hasten disease breakdown