Stem canker

Leptosphaeria maculans:

Leptosphaeria maculans is a fungal pathogen that causes the disease known as blackleg in cruciferous crops, with canola (oilseed rape) being a primary host. Here's an informative description:

Symptoms:

1. Leaf Lesions: The disease starts with the appearance of small, dark lesions on the leaves of canola plants.
2. Lesion Enlargement: Lesions can enlarge, and as the disease progresses, they may coalesce, leading to extensive damage.
3. Canker Formation: The pathogen can cause cankers on the stem, leading to wilting and lodging of plants.
4. Dark Fruiting Bodies: In advanced stages, the fungus produces dark fruiting bodies (pycnidia) on infected tissues.

Identification:

1. Lesion Appearance: Identify small, dark lesions on leaves, stems, and pods.
2. Canker Formation: Recognize the presence of cankers on stems, which may result in wilting and plant lodging.
3. Fruiting Bodies: In advanced stages, the presence of dark fruiting bodies on infected tissues can aid in identification.

Disease Cycle:

1. Survival: The fungus can survive on infected crop residues.
2. Spore Production: Spores are produced on infected residues and are spread to healthy plants by wind or rain.
3. Infection: Spores germinate and infect plants through wounds or natural openings.

Management:

Cultural Practices:

1. Crop Rotation: Rotate crops to reduce the buildup of inoculum in the soil.
2. Resistant Varieties: Plant canola varieties with resistance to blackleg.
3. Clean Seed: Use disease-free seed to reduce the risk of introducing the pathogen.

Fungicide Application:

1. Seed Treatments: Treat canola seeds with fungicides to protect seedlings.
2. Foliar Fungicides: Application of fungicides during the growing season, especially at critical stages, can help manage blackleg.

Regular Monitoring:

1. Field Scouting: Regularly scout fields for early symptoms of blackleg, especially during periods conducive to disease development.

Harvest Practices:

1. Avoiding Infected Residues: Minimize the spread of the pathogen by avoiding the incorporation of infected residues during harvest.