Hop latent viroid

Hop latent viroid (Cocadviroid latenshumuli) is a small, circular, single-stranded RNA pathogen that infects hop plants (Humulus lupulus). As a member of the Cocadviroid genus, it causes systemic infections that interfere with normal plant growth and development, often leading to reduced yield and poor quality of harvested hop cones.

The host range is largely specific to the Cannabaceae family. Once infected, the plant becomes a permanent reservoir for the viroid. The pathogen spreads throughout the plant's vascular system, concentrating in the roots and shoot tips, which makes it particularly difficult to manage once established in a perennial crop like hops.

Symptoms of infection are often subtle, which is why it is termed "latent." Growers may observe stunted shoots, shorter internodes, leaf chlorosis, and occasionally brittle stems. Infected plants show lower alpha-acid content, which directly impacts the economic value of the hop production, even if the plant survives and appears visually healthy.

Transmission occurs primarily through mechanical means. Farm equipment, pruning shears, and harvesting tools are the most common vectors of the viroid. Furthermore, because hops are propagated vegetatively, planting infected rhizomes is the most frequent way the disease is introduced into new fields, leading to rapid contamination of the entire plantation.

Prevention and management require a strict sanitation protocol. Growers should implement routine disinfection of all tools using appropriate chemical agents, source only virus-tested, certified plant material, and practice regular scouting to rogue out symptomatic plants. There is no chemical cure for viroid infections; therefore, exclusion and hygiene are the only effective tools for control.