The Citrus stubborn disease is a plant disease affecting species in the genus Citrus. Spiroplasma citri, a Mollicute bacterium species, is the causative agent of the disease. It is present in the phloem of the affected plant and transmitted by several leafhoppers including Circulifer tenellus (beet leafhopper) and Scaphytopius nitridus in citrus-growing regions of California and Arizona and Circulifer haematoceps in the Mediterranean region.