What are the control methods for Hydrangea ringspot virus?

[Distribution and Damage] Hydrangea (Hydrangea macrophylla), also known as bigleaf hydrangea, is a deciduous shrub planted throughout China. Viral infections are relatively common, with ringspot being the most frequent.

It is generally latent; severely affected plants become stunted, with few or no flowers.

[Symptoms] Leaves become crinkled, and the stems sometimes show necrotic spots. When inoculated onto diseased plants, the old leaves develop chlorotic spots, brown ringspots or oak-leaf patterns.

[Pathogen] The virus HyRSV, also belonging to the Potato virus Y group. Particles are filamentous, 470-650nm × 13nm. Thermal inactivation point 70-75°C. Dilution endpoint 10-5. Longevity in vitro 21-35 days (at room temperature). This virus has distant serological relationships with Potato virus X, Cactus virus X, White clover mosaic virus, etc.

[Disease Cycle] Hydrangea is the only natural host. Artificial inoculation can infect more than 20 plant species. Globe amaranth, Chenopodium quinoa and cucumber can serve as indicator hosts. Primrose can serve as a propagation host. Diseased perennial roots are the main source of infection. Cuttings or divisions can transmit the disease, and grafting or tools can also carry the disease.

[Control Measures] Pay attention to tool disinfection. Select disease-free mother plants for propagation, or carry out heat treatment at 38°C for 4 weeks. Breed resistant varieties.