Hop latent viroid (HLVd) in Cannabis – Symptoms, Transmission, and Management

Overview

Hop latent viroid (HLVd) is a pathogenic RNA viroid originally identified in hops (Humulus lupulus) that has since been found to infect Cannabis sativa. It is currently considered one of the most damaging pathogenic threats in cannabis cultivation, especially during clonal propagation.

HLVd causes severe economic damage in commercial grow operations and poses a hidden risk for home growers as well.

Symptoms

Vegetative Stage:

Stunted growth
Shortened internodes
Small, deformed leaves
Vein chlorosis (lightening of the leaf veins)

Flowering Stage:

“Dudding”: severely underdeveloped buds
Reduced resin and terpene production
Sparse trichomes
Weak aroma

Transmission

HLVd is mechanically transmitted:

Via contaminated tools, gloves, or direct contact
Through infected clones or mother plants
In hydroponic systems, via root exudates and shared water

Important: Recent studies confirm a significant seed transmission rate (58–84% in peer-reviewed data). Previous assumptions that HLVd was not seed-transmissible are outdated.

Diagnostics

RT-PCR or RT-qPCR is the current gold standard
Viroid titers are often low – multiple samples from different plant parts may be required
Rapid tests are not yet available for home growers in 2025 – lab-based diagnostics are necessary

Treatment and Management

Treatment:

There is no direct cure
RNAi-based approaches are being researched, but not yet available
Heat treatment and meristem culture show experimental promise but are labor-intensive

Prevention:

Use only certified viroid-free starting material
Thoroughly disinfect tools (e.g., 10% sodium hypochlorite or Virkon S)
Regularly change gloves and cutting tools
Quarantine new plants for at least 2 weeks
Test mother plants regularly and destroy infected ones immediately

Relevance for Home Growers

Because certified and lab-tested seeds are rarely available to hobbyists, the risk of unnoticed HLVd infection is high. Even seed-grown plants may carry latent infections. Thus, strict hygiene and isolation protocols are critical.