Hop mosaic

Hop mosaic is a significant viral disease caused by the Hop mosaic virus (HmMV), which is a member of the Carlavirus genus. This pathogen is known for its ability to cause systemic infection, leading to substantial economic losses in commercial hop production globally.

The primary host for this virus is the common hop (Humulus lupulus). Once a plant is infected, the virus spreads throughout its entire vascular system, interfering with metabolic processes and severely weakening the plant's overall health and vigor.

Key symptoms include a characteristic mottled or mosaic-like pattern on the leaves, often accompanied by leaf curling, distortion, and yellowing (chlorosis). Infected bines exhibit stunted growth, reduced internode length, and a marked decline in the yield and quality of hop cones at the end of the season.

Transmission occurs through several pathways, including the use of infected rhizomes or nursery stock, which is the most dangerous route for spreading the virus to new areas. Additionally, insect vectors, specifically the hop aphid (Phorodon humuli), play a critical role in spreading the virus between plants within a field or between adjacent hop yards.

Effective management requires a combination of strategies, as there is no chemical treatment to eliminate the virus once it is established in a plant. Growers should focus on planting certified virus-free rootstock, monitoring for aphids and applying necessary insecticide programs, and promptly removing and destroying infected plants to prevent the spread of the inoculum throughout the yard.