Silver nanoparticles (AgNPs) were prepared by two methods: biologically using Trichoderma viride cell free supernatant and chemically with polyvinyl pyrrolidone (PVP) using gamma irradiation. The antimicrobial activity of AgNPs was evaluated in the field against Alternaria solani which cause early blight disease of potato. Disease severity, vegetative and biochemical parameters of plant were determined. AgNPs were characterized by UV-Vis spectroscopy, FT-IR spectroscopy, Dynamic Light Scattering (DLS) and Transmission electron microscope (TEM). AgNPs had a mean diameter (12.7 nm) using biological method and (23 nm) with chemical method. Application of AgNPs 150 μg/ml + K2SO4 (2 %) as plant foliar resulted in highly effective inhibitor of disease severity that recorded (8.39 %) compared to the untreated plants (86.17 %) after 75 days of sowing. Also, a significant increase in growth and physiological parameters was recorded. Accumulation of Agᵒ in plant tissues reached minimum value. Selenium nanoparticles (SeNPs) 0.5 μg/ml, ascorbic acid 300 μg/ml and K2SO4 (2 %) reduced disease severity (9.81 %) significantly. SeNPs 0.5 μg/ml, AgNPs 150 μg/ml and K2SO4 (2 %) showed disease severity (12.63%) but all plant parameters were improved including physiological parameters and yield. It is concluded that the application of AgNPs and SeNPs are recommended as plant foliar for controlling plant pathogen and improving plant yield.