Leaf streak

Leaf streak is a fungal disease affecting various cereal crops and grasses, caused by the pathogen Scolicotrichum graminis (also known as Cercosporidium graminis). This disease primarily targets the foliage, resulting in necrotic lesions that reduce the plant's ability to undergo photosynthesis.

The disease is commonly observed on rye and various forage grasses. While it may not always be a primary limiting factor for yield, heavy infections significantly compromise the health of the crop, especially in dense stands where humidity levels remain elevated for extended periods.

Symptoms are identified by the presence of narrow, elongated necrotic streaks or spots that follow the parallel veins of the leaf. These streaks often turn brown or dark brown as the tissue dies. During periods of high moisture, the fungus produces masses of spores within these lesions, creating a visible, velvety fungal growth on the leaf surface.

The development of leaf streak is strongly influenced by environmental conditions, particularly cool to moderate temperatures and high humidity or frequent rainfall. The pathogen overwinters on infected crop residues, which serves as the primary source of inoculum for the following growing season.

To manage and prevent the spread of leaf streak, producers should focus on integrated pest management practices. Key strategies include:

• Implementing crop rotation to break the disease cycle.
• Thoroughly incorporating or destroying crop residues to reduce primary inoculum.
• Selecting resistant varieties where available.
• Applying fungicides during the flag leaf stage if disease pressure is high.