With the ever increasing demand of the crop production, technology calls for innovative ideas for better disease management leading to higher crop production with available resources. Multiple diseases caused by plant pathogens affect plant crops leads to major losses up to 30% and simultaneously decreasing the quality and safety of agricultural products. The silver nanoparticles used in the present study were prepared through a cost effective and environment friendly green synthesis technique by using leaf extract of Tagetes patula L. (french marigold) as reducing as well as capping agent. The prepared biogenic nanoparticles were well characterized using U.V. visible spectroscopy, Transmittance electron microscopy, X-ray diffraction and Fourier-transform infrared spectroscopy which revealed the size of nanoparticles ranging from 15-30nm as well revealed their cubic and hexagonal structure. Further these biologically synthesized nanoparticles were found to be highly toxic against phytopathogenic bacteria and fungi by poison food technique, disc diffusion method and spore germination inhibition test.