Combatting Crown Rot in Cereal Crops

Crown rot is a soil-borne fungal disease, most prevalent in wet conditions and heavy soils. The disease is encouraged by dry, hot springs, and, with the current high moisture profiles from the last few seasons of rain, it will be important to keep an eye out for symptoms this harvest.

What to look for:

The fungus most commonly attacks cereal crops, limiting water movement within the plant roots and stem to cause early death of the tiller. It will survive indefinitely in wet soils, grassy weeds, and infected stubbles, affecting season after season of crops.

Keep an eye out for pinched grain or whiteheads (heads without grain). These will usually be scattered across a paddock.

Yield loss will be most severe when there are good crop conditions to start the season, followed by a hot and dry finish. This is because the fungus spreads throughout the crop during the wet, and then grows rapidly in hot conditions, causing moisture stress in the plants.

In such a season, even the most tolerant varieties can suffer yield losses of 40%. The occurrence of Crown Rot has increased as a result of no-till and tight cereal rotations.

Common Symptoms:

  • Brown stem base, most obvious when the lower leaf sheaths are pulled back
  • Stunted and yellow plants
  • Single dead tillers
  • Pinkish fungal growth in moist conditions
  • Pinched grain at harvest
  • Scattered whiteheads

Oats – It can be difficult to see the brown stem base, and they rarely develop whiteheads.

Barley – Matures earlier than wheat, escaping moisture stress, so it doesn’t normally produce whiteheads. Grain quality is not highly affected.

Wheat and Durum – Screenings may increase.

“CR can cause yield loss before symptoms become obvious and symptoms are more noticeable when plants are under moisture stress.”

How to Manage and Control Crown Rot

Crown Rot management requires an integrated approach including both crop rotation and sowing techniques.

Many control strategies will help remove the fungus from above the ground, but as it is a soil-borne disease, it can take a few years of management practices to reduce the risk of high yield loss from Crown Rot.

  • Rotation management – Having a break from cereal rotations is the most effective strategy to reduce Crown Rot. These breaks are most effective when combined with proper weed control to remove grass hosts, and when supported with good rainfall to increase breakdown of disease levels. Break crops with dense foliage, like canola and sorghum, will create warm, damp conditions and quicken the breakdown of fungus in the soil.
  • Variety selection – Before planting, test the infection levels in your soil. Depending on the amount of disease present, select cereals with high tolerance – durum wheat is the most susceptible, and should be avoided. Sowing resistant varieties of cereal crops can help to limit yield loss, but growers must remain cautious as even resistant crops can suffer under heavy disease pressure and dry conditions. Where high levels of disease are present, a break crop may be required.
  • Inter-row sowing – Using inter-row sowing to sow between rows of infected stubble has been shown to reduce infection rates significantly, with up to a 50% decrease in infected plants and a corresponding yield increase of 5 to 10%.
  • Cultivation – Incorporating stubbles and crop residues into the soil can increase the speed of disease breakdown. It can still take years, depending on biological activity, soil moisture, and nutrient availability, and it is crucial to exercise caution as cultivation can also spread infected residues, potentially increasing infection rates the next season.
  • Stubble management – Baling and removing straw, and burning stubble, are both effective techniques that will remove Crown Rot from plant material above the ground. This strategy is not wholly effective though, as the fungus is primarily soil-borne, and disease below the ground will not be affected by stubble management practices.
  • Weed management – Grassy weeds can play host to this fungal disease, allowing it to live indefinitely and be passed on to cereal crops season after season. That’s why it’s important to control them in-crop and in fallow, reducing the risk of crop infection.
  • Seed treatment – Use chemical treatments to protect your cereal seeds from diseases such as Crown Rot. These should be used in combination with other management strategies. According to agronomist Rob Long “Yield loss is going to vary this harvest and we anticipate there will be paddock losses as a result of crown rot, somewhere between 5% and up to 40%.” Evergol Energy, and a yet-to-be-released chemical, Victrato, will not completely combat crown rot, but will help to suppress it.


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