Canola and Mustard: Blackleg (Leptosphaeria maculans)

Publication 812: Field Crop Protection Guide > Chapter 6: Canola and Mustard > Blackleg

Field Crop Protection Guide 2011-2012, Order 2011-2012 publication

Table of Contents

  1. Description
  2. Integrated Pest Management Options
      • thiamethoxam + difenoconazole + metalaxyl M + fludioxonil – Helix Xtra
      • carbathiin + thiram – Vitavax RS Fungicide
      • imidacloprid + carbaithiin + thiram – Gaucho CS FL
    • Foliar Treatment
      • propiconazole – Tilt 250 E
      • propiconazole – Bumper 418 EC
      • azoxystrobin – Quadris
  3. Related links...

 

Description

The first symptoms appear on the cotyledons or leaves as round-to-irregular (1-2 cm) white-to-buff lesions that contain numerous small black dots (pycnidia).

Blackleg causes round-to-irregular, white-to-buff lesions containing many black dots (pycnidia).

Figure 1. Blackleg causes round-to-irregular, white-to-buff lesions containing many black dots (pycnidia).

As the season progresses, the fungus may spread to the stem and crown of the plant, producing a canker that can girdle the stem.

Blackleg spreads to the stem, producing a canker that girdles the lower stem.
Figure 2. Blackleg spreads to the stem, producing a canker that girdles the lower stem.

Integrated Pest Management Options

Seed Treatment

There are differences in susceptibility to blackleg between cultivars. Consult with your seed company and the Ontario Oil and Protein Seed Crop Committee Canola Variety Trial Results at www.ontariocanolagrowers.ca.

Maintain at least 3 years between canola crops. Fungicide seed treatments will reduce seed-borne infection.

 
Active ingredient thiamethoxam + difenoconazole + metalxyl M + fludioxonil
Trade name Helix Xtra
Rate (product) 1.5 L per 100 kg seed
Comments For use in commercial seed treatment facilities only. Not for use in hopper-box, planter-box, slurry-box, or other non-commercial seed treatment application. Follow resistance management recommendations as stated on label.

 

 
Active ingredient carbathiin + thiram
Trade name Vitavax RS Fungicide
Rate (product) 833 mL per 100 kg seed
Comments Do not graze or feed livestock on seeded area for 4 weeks after planting.

 

 
Active ingredient imidacloprid + carbaithiin + thiram
Trade name Gaucho CS FL
Rate (product) 1.4 L per 100 kg seed
Comments For use in commercial seed treatment facilities only. Not for use in hopper-box, planter-box, slurry-box, or other non-commercial seed treatment application. Do not graze livestock on treated areas for 4 weeks after planting. Do not use mustard greens that have had Gaucho CS FL seed treatment for human consumption. Follow resistance management recommendations as stated on label.

 

Foliar Treatment

A foliar fungicide may be warranted if blackleg symptoms occur at the seedling and rosette stages or if a susceptible variety is being grown. Consult with your seed company and the Ontario Oil and Protein Seed Crop Committee Canola Variety Trial Results at www.ontariocanolagrowers.ca.

 
Active ingredient propiconazole
Trade name Tilt 250 E
Rate per hectare (product) 500 mL per ha
Rate per acre (product) 200 mL per ac
PHI* 60
Comments For use in canola only. Ground and aerial application. Apply at rosette stage, between 2nd true leaf and bolting.

 

 
Active ingredient propiconazole
Trade name Bumper 418 EC
Rate per hectare (product) 300 mL per ha
Rate per acre (product) 121 mL per ac
PHI* 60
Comments For use in canola only. Ground and aerial application. Apply at rosette stage, between 2nd true leaf and bolting.

 

 
Active ingredient azoxystrobin
Trade name Quadris
Rate per hectare (product) 500 mL per ha
Rate per acre (product) 200 mL per ac
PHI* 30
Comments For use in canola only. Apply at 2-6-leaf stage. See label for information regarding resistant strains of fungus. Plant-back interval of 30 days for broadleaf and root crops and 45 days for cereals required.

 

Related links...

 


For more information:
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E-mail: ag.info.omafra@ontario.ca
Author: OMAFRA Staff
Creation Date: 2 May 2011
Last Reviewed: 20 May 2011