Psorosis

Scientific name

[Virus] Citrus psorosis virus (CPsV); Type species of Ophiovirus genus

There are several strains of CPsV, some induce severe symptoms, and others are mild.

Other common names

Scaly bark, ringspot, citrus psorosis complex, CPsV-A, CPsV-B

Disease cycle

Psorosis is transmitted by grafting. There is some evidence of natural spread, possibly by Olpidium brassicae which transmits other ophioviruses, or by an aerial vectorvector:
an organism that does not cause diseases itself but which carries the disease-causing microorganism from one host to another
. The incidence of psorosis has been reduced in many areas by using budwood certification programs.

Symptoms

Leaf - foliar symptoms have a wide range and are best seen on young leaves nearing full expansion. Symptoms include chlorotic flecks that are irregularly distributed, leaf mottling, and round chlorotic spots. Symptoms may fade as leaves mature.

Fruit - fruit may have ring shaped chlorotic patterns.

Whole tree- the most distinguishable symptom of psorosis is the scaling and flaking of the bark on the trunk and limbs. In the early stages this shows as small pimples or bubbles that later enlarge and break up into loose scales. Wood becomes impregnated with gumgum:
complex polysaccharidal substances formed by plant cells in reaction to wounding or infection
and is stained. Psorosis B caused bark lesions that are rampant and expand rapidly sloughing off large strips of bark.

Host range

Psorosis affects most citrus species and their hybrids. Sweet orange, grapefruit and tangerines are severely affected.

Distribution

Psorosis is found throughout the citrus producing world.

Easily confused with

On the trunk citrus leprosis bark scaling symptoms can appear similar to citrus psorosis. However, the psorosis virus causes wood staining while citrus leprosis does not.