As the name suggests, Hop Latent Viroid (HpLVd) was first identified in hops. Ironically, infected hop plants are asymptomatic. In contrast, infected hemp plants (Cannabis sativa) may or may not manifest any apparent symptoms. Symptoms include stunted growth, reduced vigor, brittle stems with less flower mass and stunted trichomes. This disease is commonly known as dudding.
Viroids are the smallest known pathogens of row crops and fruit trees. Like some plant pathogenic viruses, viroids are single-stranded RNA molecules; however, viroids are smaller in size and are not encapsidated. Potato spindle tuber viroid was the first viroid that was discovered in 1971. To date, twenty-nine more viroids have been discovered and characterized.
Studies indicate that the HpLVd is mainly introduced by infected propagation material. Subsequent viroid transmission from infected to healthy plants is shown to be through horticultural practices. Such mode of transmission (mechanical transmission) is also very common in phytopathogenic viral species. In hops, transmission of HpLVd was shown to be more effective with tools (e.g. pruning shears) rather than natural abrasions caused by physical contact of individual plants. In addition, no evidence of transmission and long-distance spread of the viroid by aphids has been established.