Lolium leaf spot

The causative agent of the disease is the fungus Pyrenophora lolii (anamorph Drechslera lolii). This pathogen belongs to the class Ascomycetes and primarily affects plants within the Poaceae family. The disease is classified as a leaf spot, which can lead to significant weakening of the stand or turf.

The main host crops for this fungus are various species of ryegrass (Lolium), including perennial ryegrass (Lolium perenne) and other forage grasses. The pathogen can survive on crop residues, in the soil, and can be transmitted via seed material, posing a risk to both pasture and hay production areas.

Symptoms of infection manifest as the appearance of characteristic spots on leaves and leaf sheaths. Initially, they appear as small chlorotic points that gradually enlarge, taking on an elongated or oval shape. These spots often feature a brown or dark-colored center surrounded by a yellow halo, which is typical for fungal mycelium development within plant tissues.

• High humidity levels in the air and soil.
• Frequent fog and heavy dew.
• Temperature range between +18°C and +25°C.
• Dense stands with poor air circulation.
• Plant stress due to nutrient deficiencies.

The economic impact of Pyrenophora lolii lies in the premature senescence and death of the leaf canopy, which reduces the photosynthetic capacity of the plants. Consequently, the quality of green forage decreases, with a drop in sugar and protein content, significantly lowering overall hay yields or pasture productivity.

Protection measures include adhering to proper agronomic practices: using certified healthy seeds, timely mowing of the stand, preventing waterlogging, and applying balanced fertilizers. In intensive farming systems, systemic fungicides approved for use on forage grasses are employed if the disease pressure reaches critical levels.