Crown Rot symptoms are appearing in many cereal crops, especially those exposed to post-flowering moisture stress. Symptoms and Identification

Crown Rot is caused by the fungal disease Fusarium pseudograminearum, which affects all winter cereals and many grass weeds, particularly barley grass and annual phalaris.
The disease grows inside the stems of infected plants, reducing water uptake, decreasing yield and increasing screenings. In high disease situations, yield loss can be as high as 50%.
During periods of moisture stress, entire heads will die, appearing as scattered white-heads throughout the crop.
Many incidences of Crown Rot are misdiagnosed as Take-all, which also exhibits white-head symptoms.
White-heads associated with Take-all appear in patches, rather than isolated heads scattered throughout the paddock. Also, plants suffering from Take-all will not have stem browning symptoms.
Stem browning is the most reliable method of identifying Crown Rot. Plants infected with Crown Rot have honey-brown discolouration from the crown to the first node. Sometimes a pink colouration is also observed around the first node.
White-heads alone are not a reliable indication of Crown Rot incidence, as plants can be affected without white-heads forming. This can lead to increased inoculum levels, yield loss and screenings with no apparent symptoms.

Disease Increase

Crown Rot survives between cereal crops inside infected stubbles, or in volunteer cereals and grass weeds. Inoculum will be present as long as infected stubble remains.
Consecutive cereal crops significantly increases the level of inoculum.
Cropping systems that retain cereal stubbles and contain greater than 50% cereals in rotation are building Crown Rot levels.
Moist conditions during autumn and winter are required for infection to commence, while dry spring conditions increase white-head development and yield loss.
Wet spring conditions often mask the symptoms of Crown Rot, leading to inoculum levels increasing unnoticed. Under these conditions, yield loss associated with Crown Rot will be minor, as infected plants can access adequate moisture despite the disease burden.
Poor weed control and excess Nitrogen exacerbate moisture stress and increase yield loss associated with Crown Rot.
Dry conditions through summer and during break crops will reduce stubble breakdown, with inoculum levels remaining high leading into the next cereal crop. For this reason, a one year break between cereals is rarely adequate to reduce Crown Rot.
There is some local anecdotal observation that higher levels of Crown Rot are associated with elevated levels of soil Phosphorus (>50ppm Colwell).

Management

Any measure that increases stubble breakdown will reduce Crown Rot inoculum.
Key features for reducing Crown Rot in break crops- Non-cereal crop with grass weeds and volunteer cereals controlled - Narrow rows and adequate plant populations - Vigorous growth and dense canopy to increase stubble breakdown
In mixed farming systems, grass-free pastures provide a very effective Crown Rot break.
Burning stubble reduces above-ground inoculum levels and is one of the most effective ways to reduce disease risk in the short term, but burning will not remove inoculum below-ground level in roots and crowns.
Cultivation increases breakdown of residues, but also breaks infected stubble into smaller pieces and spreads it across the paddock. This can actually increase Crown Rot infection if followed by another cereal crop.
Inter-row sowing provides some physical separation from previous stubble, however crop rotation and stubble removal are far more effective in reducing Crown Rot than inter-row sowing.
Barley suffers less yield loss than wheat with similar infection levels, as it tends to rationalise tillers rather than losing heads or decreasing grain size. Barley also tends to mature earlier than wheat, decreasing exposure to post-flowering moisture stress.
Despite being less affected than wheat, barley often increases inoculum levels to a similar, if not greater extend. For this reason barley can provide a short term solution in high Crown Rot situations, but management of the disease must be considered within the context of the overall farming system.
One of the aims of growing canola following a brown manure legume in a continuous cropping system, is to reduce Crown Rot inoculum levels to the extent that yield loss from Crown Rot in the cereal phase is negligible.