Exocortis Citrus exocortis is a viroid disease that can infect most citrus varieties where it is latent, showing symptoms only in trifoliate orange, some trifoliate orange hybrids, Rangpur lime and some citrons and lemons. Symptoms on susceptible hosts like trifoliate orange and its hybrids, Rangpur lime and some lemons include bark scaling and stunting. On citron leaf epinasity may also be seen. Control of exocortis requires the use of budwood testing free of the disease and appropriate sanitation of all pruning and grafting tools. This is the first virus-like disease of citrus recognized and described by Fawcett.
Many citrus pathologists believe the disease to be a complex of diseases that share common symptoms.
Included in this complex are such diseases as psorosis B, which may be synonymous with citrus ringspot, concave gum, blind pocket, Impietratura and Cristacortis. The disease agent may be graft transmitted to most citrus species, however, some do not develop symptoms. Susceptible hosts such as sweet orange and grapefruit develop scaling and flaking of the bark on trunks and limbs. The wood becomes impregnated with gum forming irregular circular patterns in the trunk that are very characteristic of the disease. Severe psorosis can be very destructive causing tree debilitation and decline.