Release and germination of ascospores in Uncinula necator (Schw.) Burr. the causal agent of grape powdery mildew under two wetting conditions and at 4 and 20 ?C after 20,80,120,150 and 180 days were studied. Effectivness of different tempretures (0-35?c) in release of ascospores after 24 hours as well as the amount of release of ascospores in a time period of 0-168 hours in saturation conditions was measured. Also, pathogenicity of the mature ascospores on healthy detached leaves was investigated. The results showed that maximum release occurred after 120 days from semidry treatment (20?c) with 8 ascospores per Cm2. Maximum ascospore germination (41%) after 150 days was related to semidry condition (4?C). The mature ascospores were pathogenic on healttly leaves at 20?C indicating their probable role as a primary inoculum source. Optimum temprature for release of ascopores after 24 hours was 25?C whit maximum release occuring in saturation conditions after 36 hours.
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