Alternaria solani is a fungal pathogen that primarily affects plants, particularly tomatoes and potatoes. It is known for causing a disease called early blight, which leads to dark, circular spots on leaves and stems. This can result in reduced photosynthesis and overall plant health, ultimately affecting crop yields. The fungus thrives in warm, humid conditions and can spread through wind, rain, or contaminated tools. Effective management strategies include crop rotation, resistant plant varieties, and proper sanitation practices to minimize the risk of infection and promote healthy plant growth.