An experiment was conducted in the Research Farm of Sids. Beni Suef governorate - Egypt in 2015/2016 and 2016/2017 seasons. The obtained results showed that Planting date on 5th Nov. with the two cultivars Balady and Sids-40, recorded the highest emergence percentage after 3 weeks from planting in both seasons whereas the early planting date 25th Sep. gave the lowest emergence percentage. Light cloves weight significantly increased emergence after three weeks from planting, compared with the plants which were planted by heavy cloves weight and medium cloves weight for Balady and Sids-40 cultivars respectively in both seasons. Early planting date (Sep.25 and Oct.15) with medium and heavy cloves weight gave the highest plant height and number of leaves. Also, recorded higher mean values of bulb yield and its components, of the two tested garlic cultivars than the late planting date (Nov.5) in both seasons. Downy mildew severity was increased on Sids-40 cultivar more than Balay cultivar. The early planting in September revealed the lowest disease severity compared with November planting date, in both cultivars. No significant differences observed for the effect of clove size on disease severity, in both cultivars. The population of leaves microorganism such fungi or bacteria play a meaningful role of increasing or decreasing downy mildew severity, whereas the earliest planting increasing of the microbial population which effected on the reduced of downy mildew severity. Also, in both growing seasons, an inverse relationship between garlic clove size and disease severity of downy mildew was found.