Glume blotch

Phaeosphaeria nodorum

Phaeosphaeria nodorum, now classified as Parastagonospora nodorum, is a fungal pathogen that causes the disease known as nodorum blotch or glume blotch in wheat (Triticum aestivum) and other cereal crops. Here is an informative description of Parastagonospora nodorum, covering its appearance, identification, and management:

1. Symptoms:

  • Leaf Lesions: Nodorum blotch symptoms primarily manifest as dark brown to black lesions with a tan or gray center on the leaves of wheat plants.
  • Lesion Shape: Lesions often have a rectangular or oval shape, and they can coalesce as the disease progresses.
  • Glume Blotch: In addition to affecting leaves, the pathogen can cause lesions on the glumes of wheat heads, contributing to glume blotch.

2. Disease Cycle:

  • Overwintering: The fungus may overwinter on infected plant debris or as dormant mycelium in seeds.
  • Infection: Infection occurs through spores (conidia) produced on infected residues or seeds.
  • Spread: Conidia are dispersed by wind, rain, or splashing water, leading to new infections on leaves and glumes.
  • Favorable Conditions: Warm and humid conditions, especially during the growing season, favor disease development.

3. Identification:

  • Lesion Characteristics: Identification involves observing the characteristic lesions on leaves and glumes. Lesions on glumes may have a dark margin.
  • Conidia Production: Microscopic examination may reveal the presence of conidia, aiding in accurate identification.

4. Management:

  • Resistant Varieties: Planting wheat varieties that are resistant or less susceptible to nodorum blotch is an effective strategy.
  • Fungicide Applications: Fungicides, especially those effective against Parastagonospora nodorum, can be applied preventively or curatively. Application timing is crucial, and a rotation of different fungicide classes is recommended to reduce the risk of resistance development.
  • Crop Rotation: Avoiding consecutive cultivation of wheat in the same field can help reduce the inoculum.
  • Sanitation: Proper management of crop residues, including plowing under infected residues, can reduce the source of inoculum.

5. Importance:

  • Economic Impact: Nodorum blotch caused by Parastagonospora nodorum can lead to reduced wheat yields and affect grain quality.
  • Global Distribution: The pathogen is present in wheat-growing regions worldwide.