Biological control is an approach that provides safe fungal management program, and corresponds to a substitute for reliance on chemical treatment methods. It is often used to gradually suppress widespread infestations in low value or remote areas where other methods are not feasible. Natural plants derived compounds contribute a lot in fight against pathogens.Numerous studies conducted in Pakistan revealed a wide spectrum prospects of using extracts of plants for biological control of pathogenic fungi. On the basis of efficacy of plant extracts, present study has been designed to find out the effective plant product to control Alternaria alternata in vitro by using medicinal plant, Tagetus errectus, and molecular characterization of Alternaria alternata.