Citrus variegated chlorosis

CVC leaf
Notice the yellow discolorations in the leaves of this CVC infected orange tree

In 1987, a new disease of citrus, citrus variegated chlorosis (CVC), was recognized in the states of Sao Paulo and Minas Gerais, Brazil. It has spread rapidly in Brazil, where it causes losses to citrus production.

Symptoms. Chlorotic yellow spots appear on the leaves of affected trees. On the lower side of the leaf, lesions with extruded gum often occur opposite the chlorotic spots that are on the upper side of the leaf. Fruits are much smaller than normal and extremely firm. In comparative studies, blossom and fruit set occur at the same time on healthy and CVC affected trees, but normal fruit thinning does not occur on CVC affected trees and the fruits remain small but ripen earlier. Once a tree is affected by CVC, the growth rate of the tree slows, twigs and branches die back, and the canopy thins, but affected trees do not die. CVC affects most orange varieties, but is also seen on trees propagated on all common rootstocks in Brazil such as Rangpur lime, Cleopatra mandarin, and Volkamer lemon.

Infected orange
Healthy orange and CVC infected orange

Xylella fastidiosa and CVC. Electron microscopy has shown that bacteria associated with CVC have the morphological and structural characteristics of X. fastidiosa. Cultured isolates of X. fastidiosa from citrus trees with CVC disease were mechanically introduced into healthy trees and caused the CVC symptoms in the inoculated plants. Several detection methods have been developed to confirm the presence of X. fastidiosa in diseased trees.

Vectors. Surveys of two different citrus areas in San Paulo state has shown several species of sharpshooters occur regularly on citrus, which may explain the rapid spread of CVC within groves in Brazil. Research on vector biology and transmission of Xylella fastidiosa is underway in Brazil.

There is a nice review covering CVC in portuguese – PDF

And another one in English – CVC

Fundecitrus, a private non-profit supported by the citrus industry in Brazil, has a nice website about CVC (in portuguese) – link