Citrus stubborn disease

The Citrus stubborn disease is a plant disease affecting species in the genus Citrus. The causative agent of the agent of the disease is Spiroplasma citri, a Mollicute bacterium species. The bacterium resides in the phloem of the affected plant. Originally discovered in citrus-growing regions of California, S. citri is transmitted by several leafhoppers, including Circulifer tenellus (beet leafhopper) and Scaphytopius nitridus in citrus-growing regions of California.^: 8 The disease has now spread to Arizona by the same hoppers, and Circulifer haematoceps in the Mediterranean region.

The primary host affected by citrus stubborn disease is the sweet orange, but the bacterium can also infect weeds such as periwinkle (Vinca rosea) and London rocket (Sisymbrium irio).^: 8 Yellowed plants of Chinese cabbage and pak-choi (Brassica rapa) can be infected by S. citri. In the wild, shortpod mustard (Hirschfeldia incana) infested by the beet leafhopper, Circulifer tenellus, can prove to be an important reservoir of infection. S. citri can also be transmitted to China aster (Callistephus chinensis), Shasta daisy (Leucanthemum × superbum), red clover (Trifolium pratense) and radish (Raphanus sativus) by the leafhopper Scaphytopius nitridus. The bacterium has also been shown to experimentally infect white clover (Trifolium repens) using Euscelis incisa as a vector.

Symptoms on citrus trees are variable but typically include small size with upright position. Fruits harvested from citrus trees with severe symptoms of citrus stubborn disease can be acorn-shaped or lopsided.