Field experiments were carried out in the seasons 2017/2018 and 2018/2019 at Sids Horticultural Research Station, A.R.C. Beni-Suef governorate, under natural infection conditions of purple blotch. The purpose of this research was to evaluate the efficacy of different irrigation intervals and plant density on garlic purple blotch severity and incidence, phyllosphere microorganisms' community, vegetative characters, and productivity of garlic plants. Irrigation intervals (14, 21, and 28 days) and plant density levels (30, 45, and 60 cloves / m²) significantly affect the disease incidence and severity. Irrigation at 14 days intervals reduced purple blotch severity and incidence on garlic plants at the different plant densities followed by 21- and 28-days intervals. Meanwhile, a high population (60 plants/ m²) obtained the highest percent of purple blotch incidence and severity compared with both 30 and 45 plant/ m². On the other hand, irrigation intervals, plant density, and their interaction significantly also affected the total count of phyllosphere microorganisms as well as garlic growth parameters (plant height, vegetative growth weight, dry weights of bulbs, and loss weight percentage after 6 months).