Purple spot disease is caused by the fungus Alternaria porri Ell. Cif. which has the potential to cause damage and decrease shallot productivity by 3% -57%. Disease control in general is still emphasized by farmers regarding the use of chemical pesticides that can cause resistance to pests and diseases, and can cause pollution to the environment, even detrimental to human health. So it is necessary to have safe and friendly control for the environment, one of which is by using the biological agent Pseudomonas fluorescens Migula. The purpose of this study was to determine the effect of the concentration of P. fluorescens Migula. to suppress the intensity of purple spot disease caused by A. porri Ell. Cif. on shallots. This research was conducted from February to April 2023, at the UPTD Horticulture Seed Center located in West Java. This study used a randomized block design (RBD), consisting of 6 treatments and 4 replications. The treatment consisted of the application of P. fluorescens Migula. with a concentration of 120 ml/l water, 140 ml/l water, 160 ml/l water, 180 ml/l water, Mankozeb 3 grams/l water and control. The results showed that the application of P. fluorescens Migula. influential in controlling the intensity of the disease with a concentration of 180 ml/l of water, the best in suppressing the attack of disease A . porry El. Cif. on shallots with an emphasis on disease intensity of 76.52%.