The colloidal solution of CuNPs (3±1 nm) was investigated the potential against Phytophthora spp. which cause economically crop diseases. Under in vitro test conditions, the inhibition of Phytophthora spp. mycelia growth at three concentrations of CuNPs (10, 20, 30 ppm) after 48 hours are , and 100%, respectively. These results provided a simple and economical. | Synthesis, characterization and evaluation of copper nanoparticles as agrochemicals against Phytophthora spp.