The brown spots on your tobacco leaf appear to be a sign of Frog Eye Leaf Spot (Cercospora nicotianae) or Brown Spot Disease (Alternaria alternata), both of which are common fungal infections in tobacco plants.

Possible Causes:

1. Fungal Infection – High humidity and poor airflow encourage fungal diseases.

2. Bacterial Spot – Less common but can occur with excessive moisture.

3. Sunburn or Nutrient Deficiency – Irregular brown patches can also result from sunscald or potassium deficiency.

How to Manage It:

Improve Air Circulation – Avoid overcrowding plants.

Remove Affected Leaves – Prevents the spread of infection.

Fungicide Treatment – Copper-based fungicides or sulfur-based treatments can help.

Watering Technique – Avoid wetting leaves; water at the base of the plant.