Hop Synchytrium

The primary symptom of the disease is the development of abnormal growths or galls on the stems, leaf petioles, and root crowns of the hop plant.

These galls appear as swellings that grow in size over time, often taking on a yellowish-brown color and a rough, tumor-like texture.

Severe infection leads to the deformation of stems, which can become twisted and stunted, negatively impacting the architectural growth of the plant.

As the disease progresses, the plant exhibits signs of systemic stress, including chlorosis, leaf wilting, and overall reduction in biomass production.

In cases of heavy infestation, the root crown can be so severely damaged that the entire hop bine may collapse or prematurely die back.

The causative agent of this disease is the fungus Synchytrium aureum, which belongs to the phylum Chytridiomycota. It is an obligate parasite that requires living host tissue to complete its life cycle.

The life cycle of the pathogen involves resting spores (zoosporangia) which are extremely resilient and can survive in the soil for several years waiting for favorable conditions.

During the growing season, the fungus spreads via motile zoospores, which require a film of free moisture on the plant surface to move and infect healthy tissues.

Upon penetration into the epidermal cells, the pathogen induces hypertrophy and hyperplasy, resulting in the formation of characteristic galls.

The host range is relatively narrow, primarily targeting the common hop (Humulus lupulus) and other members of the Cannabaceae family.

Synchytrium aureum thrives in environments with high humidity and poor drainage, which are essential for zoospore movement and germination.

Frequent rainfall or heavy irrigation combined with cool temperatures creates the perfect conditions for the pathogen to establish and spread.

Densely planted hop yards with poor air circulation are particularly susceptible, as they trap moisture, preventing the foliage from drying out quickly.

The pathogen is easily disseminated through infested soil, contaminated agricultural tools, or movement of infected plant debris within the farm.

Once established in the soil, the long-lived resting spores make eradication difficult, often requiring long-term field management practices.

The primary damage is a significant decrease in hop cone yield, as the plant directs its energy toward gall formation rather than flower development.

Hop quality, which is crucial for the brewing industry, is negatively affected by the disease, leading to inferior chemical profiles and aroma characteristics.

In addition to yield loss, the disease can cause a decline in the longevity of the hop yard, requiring premature replanting of the infected areas.

• Reduced cone quantity and weight.
• Degradation of lupulin quality in hop cones.
• Increased vulnerability to secondary pests and environmental stress.
• Higher production costs due to constant monitoring and cleaning.

The inability to grow healthy bines effectively limits the economic output of the impacted hop yard for the duration of the infection.

The most effective strategy for managing Synchytrium aureum is to start with high-quality, certified disease-free planting material.

Implementing proper cultural practices, such as maintaining adequate spacing between plants, ensures better ventilation and reduces moisture accumulation.

Strict sanitation measures, including the removal and destruction of infected plant parts, are vital to stop the cycle of pathogen dissemination.

Deep cultivation of the soil after harvest helps to bury infested debris, promoting the decomposition of infected tissues and reducing the resting spore count.

Chemical control is generally considered a preventative measure; once the fungus is established inside the plant tissue, it is shielded from many contact-acting fungicides.