Salinity in the soil has increased in many areas of the world due to anthropogenic influence and global warming. Salicylic acid (SA) is being explored as a way to counteract the negative effects of salinity by upregulating plant growth and photosynthetic rate. SA is a plant metabolite released naturally as an immune response against pathogenic bacteria. Therefore, exogenous SA application may in fact cause microbial selection that is ultimately harmful to the plant by reducing species diversity. In this study, we examined how the number of culturable colonies changed under different concentrations of SA treatment. Further, we monitored relative plant health via plant growth and an assay for photosynthetic rate. As SA concentration increased, the total number of observable colonies increased dramatically while plant health deteriorated. Further, the total number of morphologies seemed to converge to one indicating a lower level of species diversity in the phyllosphere of the plant. These data suggest that microbial selection is occurring in the presence of SA which could lead to disastrous consequences for the plant in extreme weather events.