Hop Latent Viroid in Cannabis

Hop latent viroid (HLVd) is a single-stranded, circular infectious RNA that is completely dependent on its host plant’s metabolism for replication. As the name suggests, HLVd occurs worldwide in hops, but it can also infect hop’s relative, cannabis. 

How does Hop Latent Viroid affect Cannabis and Hemp Plants?

HLVd won’t kill the plant or even cause obvious symptoms of infection (i.e., curling or yellowing leaves); however plants will show subtle symptoms. HLVd will greatly reduce the quality and quantity of the flower the infected plant produces.  During the vegetative stage, plants will grow shorter with smaller leaves and tighter node spacing. Flowering plants will have smaller looser buds with much fewer trichomes. One of our clients estimated that plants infected with HLVd had half the cannabinoid content of healthy plants.

How does Hop Latent Viroid spread?

HLVd is most commonly spread via infected pruning tools, which is why cultivators should always sterilize their equipment before starting work on a new plant. HLVd can also spread through cloning when cuttings are taken from an infected mother. And because symptoms of HLVd are not obvious, it can be hard to identify infected mother plants. This is especially true when infection occurs later in the plant’s development, since stunted growth will not be as apparent. 

How can Hop Latent Viroid be Controlled?

Although HLVd can be eliminated from a cannabis or hemp plant via tissue culture, it is a long and laborious process that should only be reserved for cultivars that are critical to you business. As with most plant pathogens, prevention is key. Good sanitation practices will go a long way in preventing the spread of HLVd and all other plant pathogens. Use fresh gloves each time you handle a new plant and sterilize tools often. 

Cultivators should also screen mother plants with qPCR tests to make sure any cuttings that are taken will be virus free. Cultivators can also screen incoming clones with qPCR assays to make sure they are not introducing infected plants to their grow.