Due to the drastic climatic changes, the fresh market production of vegetables like spinach, lettuce, and arugula is shifting to hydroponic greenhouse operations. In hydroponic systems, the Pythium species is a problematic plant pathogen and can be introduced on airborne dust particles from neighboring farm fields. It causes root rot that results in stunting or yellowing of leaves. Hydroponically farmed vegetables are mostly eaten raw, so chemical control is not an option for controlling Pythium infections. In this study, I sought to investigate microbial biocontrol as a safer way to manage this challenge. To identify bacterial antagonists of Pythium, I surveyed a collection of 192 pseudomonads from a Lake Erie diatom bloom, also known to contain oomycetes, and 96 bacterial strains from soils around Wood County. Using a high throughput competitive plate assay, I have identified and sequenced nine strains of Pseudomonas fluorescens that exhibit contact-dependent killing of Pythium dissotocum (A1, A2, SP3, SP2), P. oopapillum, P. ultimum, P. heterothalicum, Saprolegnia parasitica, and several other yet to be identified Pythium isolates from commercial greenhouses around the US [TBL (isolate from butter lettuce), TLC (isolate from leaf lettuce), TA (isolate from arugula), E1 and CAL] at a lowest concentration of 4000 CFUs/ml. To address the utility of LE6_D7 as a biopesticide in a complex hydroponic mixture, 50 ml of bacterial (LE6_D7) culture (OD600 2.5) was added to a 5 L tub of contaminated nutrient solution from our experimental hydroponic system and incubated for 24 hours. Aliquots of the experimental nutrient solution treated with LE6_D7 post 24 hours were filtered and the filters were grown overnight on antibiotic V8 agar plates. LE6_D7 kills iv over 90% of the Pythium propagules in a complex hydroponic solution containing algae, other bacteria, and Pythium. Bioinformatic analysis of the P. fluorescens (LE6_D7) sequence that was used in mutation experiments, indicates that it cannot degrade cellulose, pectin/starch, and contains no recognizable animal effector proteins. LE6_D7 genome sequence revealed two complete T6SSs, and several additional genes encoding proteins predicted to be delivered into the host cytoplasm by the system. This study evaluated the potential role of T6SS in the virulence of LE6_D7 against oomycetes.