Botrytis blight of lilies

The causal agent of this disease is the fungus Botrytis elliptica, a highly specialized pathogen responsible for the condition commonly known as Botrytis blight or gray mold in lilies. It is a major economic and ornamental threat to lily growers worldwide.

The primary hosts of this pathogen are various species and cultivars of the genus Lilium. The infection is particularly devastating for commercial lily production and private ornamental gardens, where it can cause significant aesthetic and physiological damage to the foliage, stems, and flower buds.

Symptoms typically begin as small, round, water-soaked spots that rapidly expand into larger, oval-shaped lesions. These spots often develop reddish-brown or dark margins. Under humid conditions, the lesions become covered with a dense, grayish-brown fuzzy layer of fungal spores, which allows the disease to spread rapidly to adjacent plants via wind, rain splashes, or contaminated tools.

The development and spread of Botrytis elliptica are heavily favored by cool to moderate temperatures and high moisture levels, including fog, dew, or heavy rainfall. The fungus overwinters as sclerotia in infected plant debris or in the soil, and it can also persist on dormant bulbs, which serve as a primary source of infection in the following growing season.

The harm caused by the disease is significant, as it leads to defoliation, stunted growth, and the loss of floral buds, which directly impacts the bulb's ability to store energy for the next year. Effective management strategies include:

• improving air circulation by adequate spacing of plants;
• careful sanitation by removing and destroying all infected plant materials;
• avoiding overhead irrigation to keep foliage dry;
• applying timely fungicide treatments using systemic or protectant products.