Leifsonia, a genus within the Microbacteriaceae family, is relevant to plant pathology, notably through species such as Leifsonia xyli subsp. xyli, which is the causal agent of ratoon stunting disease in sugarcane and related grass crops. This chapter covers Leifsonia’s ecological resilience and taxonomy, highlighting their capacity to adapt to adverse conditions and gaining them a name “terrabacteria.” Leifsonia xyli subsp. xyli has been given special attention, with an explanation of its pathogenic processes and illness symptomatology. Other Poaceae plants that are affected by disease symptoms beyond sugarcane are also included. Symbiotic interactions that promote plant development and pathogenic capabilities that affect agricultural stability are only two of the many aspects of Leifsonia biology that are highlighted in this chapter along with diagnostic procedures for accurate identification and disease control measures.