Leptosphaeria maculans

Fungal Disease

Blackleg, also known as Aerial Stem Rot, is a fungal disease caused by Leptosphaeria maculans (syn. Phoma lingam) that affects cauliflower and other brassicas. The disease thrives in wet, windy conditions and can cause severe damage, leading to stem cankering and plant death. Its spores can survive for years in crop debris and spread rapidly through farm equipment, water splash, and wind.

Symptoms of Blackleg Disease

Stem Lesions: Brown, sunken lesions that girdle the stem, causing wilting or plant death.

Root Lesions: Lesions extend below the soil and attack roots

Leaves: Yellowing between veins, turning brown and curling at the edges

Tuber Rot: Rot starts at the stem end, becoming slimy and foul-smellingC

Causes and Spread

Seed Transmission: Fungus can be carried on or inside seeds. Water and Wind: Spores spread through irrigation, rain splash, and wind. Farm Equipment: Machinery can transmit spores. Crop Debris: Fungus survives in crop residues for up to three years.

Favorable Conditions

Temperature: 18°C to 27°C.

Environment: Wet, humid, and windy condition.

Prevention and Control

Disease-Free Seeds: Use disease-indexed, certified seeds

Weed Control: Remove cruciferous weeds and volunteer plants

Debris Management: Plow under and destroy crop debris promptly after harvest

Crop Rotation: Avoid planting brassicas consecutively in the same field

Water Management: Avoid overhead irrigation

Fungicide Application: Use appropriate fungicides as a preventive measure

Effective management of blackleg disease requires a combination of preventive strategies and timely action. Maintaining clean fields, using certified seeds, and proper crop rotation are crucial to minimizing the disease's impact and ensuring a healthy cauliflower crop.