Avocado sunblotch viroid (ASBVd) (Avsunviroidae; Avsunviroid)
Pathogen
The pathogenic cause of the disease is the Avocado virus sunblotch viroid (ASBVd). Due to latent infections the disease can be a very serious problem, reducing yields by up to 20%. Transmission of the pathogen can take place through inoculations and natural root inoculations in the field, the seed, and less often it is transmitted during pruning and pollen of affected trees. It is worth noting that trees carrying the disease but not showing symptoms can transmit the pathogen through seed at rates of up to 100%, while symptomatic trees can occasionally transmit the pathogen through seed.
Symptoms
Appearance of reddish, yellow or white streaks slightly serrated along the green twigs or young stems. The main symptoms on fruits appear as white or yellow spots on fruits areas of scarring/camellia. Characteristic symptoms of the disease are also cracks in the bark in the form of alligator skin on the trunk and large branches. Diseased trees may show tree dwarfism with sparse foliage, downward branch folding. All trees with or without symptoms have significant production losses. The symptoms of the disease vary depending on the variety, the environmental conditions and the viral strain.
Manage
The primary measure is the use of healthy propagating material (cuttings, seeds). Frequent plant health checks are essential as non-compressively diseased trees transmit the disease more easily pathogen, while infected trees should be removed. The avocado orchards for seed production should be isolated from commercial orchards. The disinfection of tools pruning/harvesting tools help to limit the transmission of pathogen.
Area of observation
Regional section Chania and Rethymnon
