Abstract:To elucidate the resource of Ampelomyces quisqualis in the Qinling Mountains and to provide the testimony for the latent biocontrol agent selected for controlling the powdery mildew of the plants, the natural distribution and biological characteristics of A.quisqualis were quantified in naturally occurring powdery mildew fungi collected in the Qinling Mountains between 2002 and 2003. A total of 1145 samples was studied and 39 parasites were found. These samples sourced from 21 host plant families which included Convolvulaceae, Umbelliferae, Labiatae, Compositae, Plantaginaceae, Polygonaceae, Cruciferae, Leguminosae, Commelinaceae, Balsaminaceae, Cucurbitaceae, Malvaceae, Scrophulariaceae, Rosaceae, Euphorbiaceae, Solanaceae, Celastraceae, Vitaceae, Lardizabalaceae, Aceraceae, Papilionatae, etc. The biological characteristics of some isolates under different temperatures, acidities, carbon and nitrogen were tested. The results showed that the proper growth temperature for the isolates was 20℃ and the optimum carbon and nitrogen sources were Glucose and L-Glycine, respectively. This investigation indicated that there are plentiful resources and physiological species of A.quisqualis in the Qinling Mountains. It also supplied proofs for the biocontrol agents’ development from abundant isolates.