Occurrence Patterns and Control Methods of Lily Leaf Blight

Lilies originate from the eastern and central regions of China. They are relatively cold-tolerant, prefer strong light, and do not tolerate shade. Insufficient light will affect growth and flowering. A well-drained sandy loam rich in organic matter is suitable. Their disease resistance is poor, and they are susceptible to disease under high temperature and high humidity conditions. Lily plants are upright and elegant, with large, brightly colored flowers and many varieties. They are suitable for planting in patches or clumps at the edges of lawns or for forming flower borders, creating a quiet and harmonious effect. Lilies are also treasures for potted flowers and cut flowers.

Lily leaf blight, also known as lily gray mold, affects the plant's photosynthesis, hinders growth, and reduces ornamental value. When the disease occurs severely, it causes the entire plant to die.

Symptoms: The affected parts are mainly leaves, stems, buds, and flowers. In the early stage of the disease, chlorotic spots appear on infected leaves, and later the lesions expand into circular or elliptical shapes, ranging from light yellow to reddish-brown. Some lesions have a light gray center with purple edges. When dry, the lesions dry up and turn light gray. In the late stage of the disease, the leaves wither and die. When the stem is infected, the diseased part turns brown and breaks. When buds and flowers are affected, they turn brown and rot. When young plants are affected, the growing point dies. When humid, gray mold-like substances are produced on the diseased parts, which are the conidiophores and conidia of the pathogen.

Pathogen: The pathogen is Botrytis elliptica (Berk.) Cooke, belonging to the Deuteromycotina, Hyphomycetes, Hyphomycetales, and the genus Botrytis. Sclerotia occasionally form on bulbs, but are commonly found on flowers that fall to the ground in summer.

Occurrence patterns: The pathogen overwinters as mycelium and sclerotia on diseased plants and plant debris. In the following spring, the overwintered mycelium and sclerotia germinate to produce conidia, which spread to plants through wind and rain, causing primary infection. Under suitable conditions, multiple infections can occur within a single growing season, and finally the pathogen enters its overwintering sites. Under cool, rainy, dewy, and foggy humid conditions, the pathogen produces large numbers of conidia. When air humidity is saturated and the temperature is 16°C, conidia germinate most rapidly; when the temperature is 10-18°C and there is foggy, humid weather, the pathogen can easily complete infection, and new conidia can form again within a few days.

Control: ① Reduce sources of infection: Bud removal, flower thinning, and the removal of diseased leaves and old leaves should be immediately collected and deeply buried or burned. At the end of the growing season, diseased plants and all plant debris should be collected and deeply buried or burned. ② Strengthen cultivation management: In greenhouses, ensure ventilation to reduce humidity and provide sufficient sunlight. ③ Chemical control: During the disease period, spray 1:1:100 Bordeaux mixture or 50% zineb wettable powder at 800-1000 times dilution, once every 10-15 days, spraying 2-3 times.