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Proper management can shield canola from blackleg.

Agronomy Bulletin 87 ─ Canola Blackleg

Canola blackleg is identified by its gray lesions.

Situation

Blackleg can be found in most canola fields throughout the northern Plains and much of North America. Though the disease is common, diligent growers can overcome its effects.

Factors to Consider

  • Disease cycle
  • Crop rotation
  • Hybrid selection
  • Fungicides

Action Plan

  1. Consider disease cycle. Blackleg is caused by the fungus Leptosphaeria maculans, which can survive for several years on crop residue. Aerospores cause new infection, especially during wet conditions with temperatures from 70 to 79 F. Infection usually is marked by gray lesions with a dark border and is most common in the four- to six-leaf stage.
  2. Rotate crops. Build a four-year crop rotation program to reduce blackleg infections. Chopping and spreading canola stubble will break down residue faster.
  3. Select resistant hybrids. Blackleg can be sourced from infected seed. Premium seed treatments can limit early blackleg development. Choose canola varieties and hybrids based on their known tolerance to blackleg.
  4. Control disease spread with fungicides. Regularly scout canola fields. If blackleg is suspected, check risk factors such as recent disease history, susceptibility of the variety and the plant growth stage. If a fungicide treatment is warranted, consult your state’s fungicide guide for the latest fungicide recommendations.

Summary

Blackleg poses a serious threat to all North American canola growers, but effective management can help prevent serious losses. For more information about canola blackleg, contact your local Mycogen Seeds customer agronomist or trusted agronomic adviser.

Published on Wednesday, July 31, 2013