Spiroplasma citri

Spiroplasma citri is a mycoplasma-like organism (MLO) causing citrus stubborn disease, an economically significant disease affecting citrus production worldwide, particularly in Mediterranean regions and warm climates. The pathogen causes stunting of citrus trees, reduced fruit size and quality, chlorotic patterns on leaves, and overall tree decline reducing productivity and orchard lifespan. S. citri is transmitted by the leafhopper vector Scaphytopius nitridus through persistent propagative transmission, meaning the insect vector must maintain the pathogen through molts for transmission to be possible. Infected trees show characteristic symptoms including yellow blotchy patterns, fruit deformation, and premature senescence. Nursery-grown citrus trees can become infected and spread the disease to new orchards if not properly screened. No cure exists for infected trees requiring removal and replanting with disease-free stock.