Citrus stubborn disease

Citrus stubborn disease
Common names CSD, citrus stubborn, little leaf disease of citrus, stubborn disease of citrus
Causal agents Spiroplasma citri
Hosts Sweet orange
Vectors Leafhoppers (Circulifer tenellus (beet leafhopper), Scaphytopius nitridus, Circulifer haematoceps)
EPPO code SPIRCI
Distribution California and Arizona, Mediterranean region

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.[1] 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.

The host most notably affected is sweet orange but the bacterium can also infect weeds such as periwinkle (Vinca rosea) and London rocket (Sisymbrium irio).[2][3] 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.[4] The bacterium has also been shown to experimentally infect white clover (Trifolium repens) using Euscelis plebejus as a vector.[5]

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.

Symptoms

Symptoms of Citrus Stubborn disease are most prominent in immature plants but still appear on established trees. The primary symptom of Citrus Stubborn disease is the irregularity of fruit on the same tree. One tree may have fruits of differing sizes, shapes, and stages of maturity. This symptom would be indicative to farmers that their crop may have been infected with Spiroplasma citri.

Other indications of infection by Spiroplasma citri include smaller leaves and bunchy growth of branches. Citrus stubborn disease will cause the branches to appear clustered together with a more vertical orientation, compared to healthy plants with outstreched branches. Fruits may drop from the tree while they are still very small and underdeveloped and also may be lopsided or acorn shaped. A tree with Citrus Stubborn Disease will have a very low yield and the fruit it does yield will not be comparable to a healthy fruit. Small leaves and upright, bunchy growth of branches is common in infected plants, as is dieback.

See also

References

  1. ↑ Polymerase Chain Reaction-Based Detection of Spiroplasma citri Associated with Citrus Stubborn Disease. Raymond K. Yokomi, Alexandre F. S. Mello, Maria Saponari and Jacqueline Fletcher, Plant Disease, February 2008, Volume 92, Number 2, pages 253-260, doi:10.1094/PDIS-92-2-0253
  2. ↑ Leafhoppers transmit citrus stubborn disease to weed host. George H. Kaloostian, George N. Oldfield, Edmond C. Calavan and Richard L. Blue, California Agriculture, September 1976, Volume 30, Number 9, pages 4-5, doi:10.3733/ca.v030n09p4
  3. ↑ Occurrence of Spiroplasma citri in periwinkle in California. A.L. Granett, R.L. Blue, M.K. Harjung, E.C. Calavan, D.J. Gumpf, California Agriculture, volume 30, issue 3, pages 18-19, doi:10.3733/ca.v030n03p18
  4. ↑ New hosts of citrus stubborn disease. Oldfield G.N., Kaloostian G.H., Pierce H.D., Sullivan D.A., Calavan E.C. and Blue R.L., Citrograph, 1977, Volume 62, Number 10, pages 309-312 (abstract)
  5. ↑ Spiroplasmas are the causal agents of citrus little-leaf disease. P. G. Markham, R. Townsend, M. Bar-Joseph, M. J. Daniels, A. Plaskitt and B. M. Meddins, Annals of Applied Biology, September 1974, Volume 78, Issue 1, pages 49–57, doi:10.1111/j.1744-7348.1974.tb01484.x

External links

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