Anther smut of squill

The fungus Antherospora vaillantii is an obligate pathogen responsible for anther smut, a disease that specifically targets the floral organs of host plants. Formerly classified within the genus Ustilago, it is now recognized as a distinct species that significantly impacts the reproductive success of susceptible host populations.

Host plants for Antherospora vaillantii primarily include members of the Asparagaceae family. Common ornamental bulbs such as Scilla (squill), Galtonia, and Ornithogalum (star-of-Bethlehem) are frequently susceptible. The pathogen is often found in botanical gardens and ornamental landscapes where these species are grown in close proximity.

The primary symptom of the infection is the replacement of pollen grains within the anthers by a dark, sooty mass of fungal teliospores. As the flower opens, the anther walls rupture, releasing the spores, which coat the flower's interior. This process renders the plant sterile and diminishes its aesthetic and ecological value.

Environmental conditions that favor high humidity and moderate temperatures often accelerate the spread of the disease. The fungus typically survives as mycelium within the infected bulb tissues throughout the winter, ensuring that the pathogen persists in the same plant year after year as it enters its new growing season.

Management strategies focus on the removal of infected plants to prevent spore dispersal. Because the fungus is systemic, simple pruning is ineffective, and the entire plant including the bulb must be excavated. To prevent outbreaks, growers should practice strict sanitation, avoid crowded planting conditions, and utilize certified disease-free bulbs for propagation.