Broad disease constraint resources are outlined in the Agronomists Toolkit. Specific disease categories are listed below:

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Alternaria leaf and pod spot

Constraint - Alternaria leaf and pod spot

Description

  • Alternaria is usually caused by the fungal pathogen Alternaria brassicae 

  • Severity varies between years and locations depending on seasonal conditions

  •  If infected seed is sown, seedling blight may occur 

Symptoms

  • Alternaria infects all growth stages of canola plants, however plants from mid flowering onwards are most susceptible 

  • Spots develop on leaves, pods, and stems, and are brown, black, or greyish white with a dark border

  • Lesions on green leaves are often surrounded by a chlorotic halo

  • Severe pod infections may cause seed to shrivel and pods to prematurely ripen and shatter

Damage

  • Yield loss is unusual and is normally associated with the shattering of infected pods

  • Seedling blight from using infected seed may also reduce yield

Management

Alternaria is very common in canola crops but is not usually severe enough to warrant control. In Australia, there are no registered fungicide seed treatments for alternaria. Controlling grass weeds, removal of infected canola stubble, sourcing of clean disease free seed, and ensuring that canola is far removed from last years canola stubble if alternaria was present are all ways to reduce the risk of alternaria occurence. 

 

 

Links and Resources

AOF - Alternaria

Page 39. Information on description, disease symptoms, damage, and management.

DEPI VIC - Canola diseases Alternaria

The section on alternaria contains information on introduction, symptoms, disease cycle, and management. Published 2008, page last updated 2009, reviewed 2010.

DEPI VIC - Identification and management of field crop diseases in Victoria. Alternaria

Page 146. Table 11.1 gives a key for canola diseases at different stages of plant growth. Page 151 contains introduction, symptoms, disease cycle, and management. Published 2012.

GRDC - Best Practice Management Guide. Alternaria

Pages 59 and 63. Common diseases of canola table, and introduction, symptoms, disease cycle, and management. Published 2009.

Victorian winter crop summary 2014 - Alternaria

Page 45. Table 1: Canola disease guide summary. Description of organism, symptoms, occurrence, inoculum source, and control. Updated annually.