Hop latent virus

Hop latent virus (HpLV) is a widespread phytopathogen primarily infecting the common hop (Humulus lupulus). It belongs to the genus Carlavirus and is characterized by its ability to cause asymptomatic or mild infections in host plants. Despite the lack of overt symptoms, the virus is widespread in many hop-growing regions worldwide, posing a silent threat to crop productivity.

The host range of HpLV includes the hop plant and occasionally some other species within the Cannabaceae family. The virus consists of flexuous filamentous particles containing a positive-sense single-stranded RNA genome. Because the infection is often systemic and latent, it can persist in rhizomes for many years, meaning that propagation of infected material leads to the spread of the virus to new plantations.

The biological cycle of HpLV is largely dependent on insect vectors, primarily aphids such as Phorodon humuli. Transmission occurs in a non-persistent manner, where the virus is acquired by the aphid during brief probes on infected plant tissue and then transmitted to healthy plants during subsequent feeding. Mechanical transmission can also occur through pruning shears or other equipment if proper sanitation is not maintained.

Development and spread are facilitated by environmental conditions that favor high populations of aphid vectors. When weather conditions are favorable for aphid activity, the rate of transmission within a hop yard can increase significantly. Since the virus is not soil-borne but is easily maintained in the perennial rootstocks, it poses a long-term risk to the longevity and profitability of commercial hop yards.

The economic impact of HpLV is largely associated with reduced yield, lower alpha-acid content, and poor overall plant vigor. While it rarely kills the plant outright, the chronic stress caused by the virus makes the hop plant more susceptible to secondary infections and environmental stressors. Effective management is essential to maintain the quality and quantity of the hop crop in high-yielding varieties.

• Utilize only virus-indexed, certified disease-free hop planting material.
• Implement rigorous aphid control programs during the growing season.
• Sanitize pruning and cultivation tools between individual plants.
• Conduct regular inspections to identify and rogue out symptomatic plants.
• Establish isolation buffers from older, potentially infected hop fields.