Barley net blotch

Helminthosporium teres

Causal Agent: Helminthosporium teres is a fungal pathogen that causes barley leaf blotch, a foliar disease affecting barley (Hordeum vulgare).

Symptoms:

  1. Leaf Lesions:

    • Oval Lesions: The primary symptom is the development of oval-shaped lesions on the leaves.
    • Gray to Tan Centers: Lesions often have a gray to tan center with a dark border.

  2. Leaf Blighting:

    • Coalescing Lesions: As the disease progresses, lesions may coalesce, leading to extensive blighting of the leaves.
    • Reduced Photosynthesis: Severe infections can impact photosynthesis, affecting overall plant health.

  3. Culm and Sheath Infections:

    • Lesions on Culms and Sheaths: In addition to leaves, the fungus can infect culms (stems) and sheaths, contributing to the overall decline of the plant.

Identification:

  1. Distinctive Lesions:

    • Oval lesions with gray to tan centers and dark borders on leaves, culms, and sheaths.

  2. Favorable Conditions:

    • Humidity and Rain: The disease thrives in humid conditions, and rain can facilitate spore dispersal.

Conditions Favoring Disease:

  1. Humid Conditions:

    • Moisture Facilitates Spore Production: Helminthosporium teres produces spores in the presence of moisture, and high humidity favors disease development.

  2. Moderate Temperatures:

    • Optimal Growth Conditions: Moderate temperatures, typically ranging from 15 to 25 degrees Celsius (59 to 77 degrees Fahrenheit), are conducive to the growth of Helminthosporium teres.

Management:

  1. Resistant Varieties:

    • Plant Resistant Cultivars: Select barley varieties that exhibit resistance or tolerance to Helminthosporium teres.

  2. Fungicides:

    • Foliar Applications: Application of fungicides may be considered in cases of severe infections. Consult with local agricultural extension services for appropriate recommendations.

  3. Crop Rotation:

    • Reduce Inoculum Buildup: Practice crop rotation to reduce the buildup of the pathogen in the soil.

  4. Sanitation:

    • Remove Infected Debris: Promote sanitation by removing and destroying infected plant debris.

Note: Barley leaf blotch caused by Helminthosporium teres can lead to significant yield losses in barley crops. Implementing integrated disease management strategies, including resistant varieties, fungicides, and cultural practices, is crucial for effective control.

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