Abstract: A newly discovered fungal pathogen isolated from the green peach aphids, Myzus persicae, in Fujian was identified as Zoophthora occidentalis.Its elongate ovoid primary conidia sized (23.4-31.2) μm× (7.8-10.9) μm (L/D =2.4-3.8) and had a clear spore collar.Secondary conidia liked primary (15.6-25.4) μm× (7.8-10.4) μm (L/D =2.46-4.08) was also oblong in shape (15.6-25.4) μm× (7.8-10.4) μm with an L/D ratio of 2.46-4.08.The size of its capilliconidium was (20.8-29.9) μm× (6.0-10.4) μm (L/D =2.4-3.6) , and the stipe was 36.4-104.0μm long.The diameter of its mycelium was 6.5-8.8μm.Its resting spores were smooth, colorless and transparent with a diameter ranging from 23.9μm to 29.9μm.Most of the infected aphids were killed in the 4th day, and green peach aphids to induce a peaked death rate in 4days and cumulative mortality ranging from 5.4%to 95.7%, which increased with the spore concentration.The resulting data fitted well on a time-dose-mortality model.The LD50 after 4days estimated by the model was less than 10conidias·mm-2, indicating the entomophthoralean fungus to be a potent pathogen for M.persicae.