Blackleg

Leptosphaeria maculans

The most important and damaging fungal disease of canola, causing severe damage and plant death through both stem canker and root rot.

Description

Blackleg survives between seasons as black, raised fruiting bodies on stubble. Spore release is then triggered by autumn rainfall – the higher the rainfall, the earlier the release. Once the spores land on seedling canola, the plants develop off-white lesions containing new, small black fruiting bodies which themselves release further spores. After stem extension there will be internal blackening at the base of the stem, but the most obvious symptoms of the disease are cankers at the base of the plant, lodging of plants and premature death of infected plants.

Control

Sowing canola varieties with good blackleg resistance ratings is the best first line of defence against the disease. The current ratings of all available varieties can be checked at australianoilseeds.com.

If the previous year’s crop was infected, disease pressure on the new season’s canola can be substantially reduced by planting it at least 200 metres and preferably more than 500 metres away from the old crop’s stubble.

Seed treatment with Jockey® Stayer® will provide further suppression of the disease, while foliar sprays of Prosaro® can deliver very effective control up to the 6-leaf crop stage.

Related Pests

Sclerotinia rot

Sclerotinia sclerotiorum

An unpredictable fungal disease that can cause severe yield losses in canola crops if wet conditions during flowering lead to high levels of infection.

Powdery mildew

Powdery mildew affects grapes and apples and is one of the most widespread, persistent and damaging fungal diseases in both Australian vineyards and apple orchards.