Citrus tristeza virus (CTV) is transmitted by several aphid species in a semi-persistent manner with Toxoptera citricida, the brown citrus aphid (BrCA), being the most efficient. Is graft-transmitted, but not transmitted through seed.
There are three different syndromes of CTV infection: stem pitting, quick decline, and seedling yellows.
Quick decline-> the flow of photosynthetic products from the upper portions of the tree down to the roots and water and nutrients adsorbed by the roots and transported up the tree are blocked, leaving fruit shriveled on the tree and leaves brown and dehydrated. In this case is a three-component malady consisting of a specific scion [sweet orange variety] and a specific rootstock [sour orange] .
Severe strains of CTV cause symptoms such as stem pitting and seedling yellows, regardless of the rootstock. Pits in the wood can be observed ranging from short and narrow to elongated and deep; gum is sometimes associated with the pits. Trunks may be so severely impacted that they have a ropey appearance. Severely affected trees are chlorotic, stunted, and generally have a low yield of poor quality fruit.