Boxwood blight (Volutella)

Boxwood blight, caused by the fungal pathogen Pseudonectria buxi (syn. Volutella buxi), is a prevalent disease affecting Buxus species worldwide. It primarily targets the foliage and stems, leading to severe defoliation and the dieback of branch tips, which significantly compromises the plant's aesthetic value and health.

The fungus is host-specific to boxwood plants. It is particularly devastating in nurseries and landscaped areas where plant density is high and air circulation is restricted. Once the fungus establishes itself within the plant tissue, it can remain latent until environmental conditions become conducive to rapid spread and infection.

Symptoms typically manifest as yellowing or browning of leaves, followed by dieback of current-year growth. A diagnostic feature of the disease is the presence of salmon-pink, cushion-like sporulating structures on the undersides of leaves and on the bark of infected twigs, usually appearing during periods of high humidity or wet weather.

Environmental conditions play a critical role in the development of Pseudonectria buxi. High moisture levels, such as those caused by frequent rainfall or overhead irrigation, facilitate the production and dispersal of spores. The fungus survives the winter on fallen leaves and dead twigs within the canopy, serving as a primary source of inoculum for the following season.

Management strategy relies on an integrated approach focusing on cultural practices and chemical control. It is vital to prune out dead or diseased branches to reduce the inoculum level and improve ventilation. Fungicide applications containing copper or systemic compounds should be utilized preventively, especially during rainy weather, to protect new growth and manage the spread of the pathogen.