Hop Latent Viroid Contamination Facts

Four methods of spread of Hop Latent Viroid in high THC Cannabis sativa.

The frequency of viroid spread has been studied recently in high-THC cannabis strains. The most spread is from infected clones taken from infected mother plants. We have seen 100% occurrence of Hop latent viroid in rooting clones taken from 3 strains of infected mother plants.

The second-most likely source is from seeds harvested from infected flowering plants confirmed to contain the viroid. This can occur at frequencies of 5% to 35%, again depending on the level of initial infection in the flowering plant.

The third likely source of the viroid is through infected sap on contaminated tools used to prune plants or obtain cuts. Here, the spread occurs from the cut stem down into the roots within 2 weeks, and then up to the rest of the plant in 4-6 weeks. This can effectively spread the viroid between mother plants or vegetative plants, later giving rise to more infected plants.

A fourth method of spread is from infected roots in a hydroponic system or from root-to-root contact or recirculating nutrient solution containing the viroid. There is no evidence yet of spread simply by gently touching plants or through insect feeding. Management practices should target the most likely methods of Hop latent viroid spread.

Therefore, viroid-free mother plants, testing of clones and seeds, and clean tools are highly recommended.

Zamir Punja

Professor, Plant Biotechnology

Simon Fraser University