The Hop Latent Viroid is a latent viral disease that affects the hop plant. Initially, it was thought that this virus didn't produce any symptoms and led to the term "latent" being incorporated into the viroid name. Research has shown that HPLVD emerged in other species besides hops, due to the increase of indoor cultivation and vertical farming operations in the UK. Imported cuttings are becoming very popular in the UK which leads to contamination of these different viruses.
HPVD has a number of symptoms, including smaller plant size and decreased plant yield, up to 30-50% decreased plant yield and malformed leaves. The plants are usually very brittle. The stems break very easily. The plants are usually diagnosed during the training stage in vegetative growth.
HPLVD is spread by contaminated tools, manure, or propagation material. The virus is spread quickly through the movement of infected plants and can remain in soil indefinitely. The plant virus can be passed on when cuttings are taken from infected mother plants; at the same time as taking cuttings from healthy plants. When pruning or trimming the plants. Infected sap can easily transfer from plant to plant. The viroid is thought to remain in the soil for many years after infection and recommendations around planting stock rotation include avoiding reusing fields that have been infected. There is no known method of killing HPLVD, other than by destroying the infected plant. Cutting infected plants results in the virus remaining on tools, which can then transfer infection to healthy plants and their new shoots.
Plant virus diseases can be fatal for your plants, but there are ways to prevent and protect against them. If you’re buying genetic imports, ask breeders and distributors whether the seeds have been tested for HPLVD. If not, then you should ensure that all scissors and trimming tools are thoroughly sterilised before moving on to another plant to avoid the risk of cross-contamination. If you are growing outdoors and have a known seed supply in the area, make sure they’re tested regularly as well.
If HPLVD is suspected, your grow room must be sterilized, and any infected plants removed. The virus can live for up to five days on surfaces such as wet walls or floors in the infected room.