Marasmius sheath and shoot blight

Pathogen and disease type: Marasmius sheath and shoot blight is a fungal infection caused by the basidiomycete Marasmiellus stenophyllus. It is classified as a parasitic disease that specifically targets the leaf sheaths and stalks of the host plant, leading to necrosis and weakened structural integrity of the crop.

Host range: The primary host for this pathogen is sugarcane (Saccharum officinarum). While it is specifically adapted to the growth environment of tropical sugarcane plantations, it can occasionally affect related grass species in highly humid environments where the inoculum pressure is high.

Symptoms and signs: The most recognizable sign is the presence of white to creamy mycelial growth on the leaf sheaths tightly wrapped around the cane stalk. As the disease progresses, these sheaths become necrotic and dry out prematurely. Severe infections can result in the fungus colonizing the shoot tissue itself, causing stunted development and sometimes the death of the primary shoot.

Development and spread conditions: The disease flourishes in high-moisture environments with prolonged periods of leaf wetness and warm temperatures. Poor canopy ventilation, often resulting from overcrowded planting densities, significantly increases the risk of the pathogen spreading rapidly throughout a field through contact or water-borne spores.

Damage and management: The blight causes economic losses by reducing the total millable cane yield and lowering sugar recovery rates. Effective management involves the use of resistant cane varieties, maintaining optimal row spacing to ensure good airflow, and implementing strict sanitation practices, such as removing infected crop debris, to reduce the primary inoculum load in the field.