Lactobacilli are well known for their beneficial effect on health. Probiotics based on lactobacilli are used for enrichment and correction of microbiome of human and animals. But could these microorganisms be used to improve plant health? Organic agriculture needs safe biofertilizers and biopreparations for crop treatment. Could lactobacilli substitute or complement other microorganisms traditionally used for plant stimulation and protection? How long could they survive on plants? What is their source? Could they form developed biofilms on plant surfaces? Are Lactobacillus spp. antagonistic to other plant microbiota representatives? A monograph elucidates the main literature data and the results of investigations of our team on biology of lactobacilli inhabiting plants. Potential of Lactobacillus to protect plants against some phytopathogens is discussed. This book will be interesting for microbiologists, biotechnologists, plant pathologists - specialists and students.