What are the main common diseases of lilies?

(1) Lily leaf blight, also known as lily gray mold, is a widespread disease. It mainly damages leaves, but can also infect stems, buds and flowers. Leaf spots are round or oval, varying in size, light yellow to light reddish brown, and water-soaked. Under warm and humid conditions, the spots become thin and brittle, light gray, and semi-transparent, and in severe cases can cause the whole leaf to die; infected stems turn brown or become constricted, causing the plant to collapse; when young plants are infected, the growing points of stems and leaves become soft and rot and die; infected flower buds initially show small brown spots, which then expand and cause the buds to rot. Under humid conditions, the diseased parts produce abundant gray mold. The pathogen mainly overwinters as sclerotia left in the soil and as mycelium on diseased residues. In the following spring, the overwintered mycelium produces gray mold on the diseased parts or on the sclerotia, and conidia spread through the air to cause primary infection. Conidia on diseased parts of field plants spread rapidly through wind and rain. The optimum growth temperature for this fungus is 22-25°C. Generally, when there is a lot of rain in early June, heavy fog and dew, and field RH90%, the disease spreads relatively quickly.

(2) Plants with lily viral disease show mosaic symptoms, with mottled patches alternating light green and dark green. Severely affected plants are noticeably dwarfed, with shorter scales, and some develop brown and necrotic spots. According to surveys, the occurrence of viral disease is closely related to the source of the seed stock; some locally saved seed stock has not been virus-free, while another portion was introduced from the Netherlands. The bulbs were very expensive, but the virus was still very severe, and viral disease in planted lilies is generally above 30%.

(3) Bulb basal rot mainly damages the base of the stem of lily plants, affecting plant growth and leading to the death of the whole plant. This disease is relatively common in many areas, with an incidence generally of 10%-15%, and as high as 10%-30%. It usually begins when the plants flower, with the plant base turning dark brown and rotting, leaves drooping and turning yellow, ultimately leading to death. The pathogen overwinters in the soil with diseased residues and becomes the primary infection source of the disease. Waterlogged soil, heavy clay soil, application of incompletely decomposed manure, and damage by nematodes and soil-dwelling pests easily lead to the disease. This fungus requires relatively high temperature and humidity, so the disease often breaks out suddenly in the middle and late stages of plant growth, when temperatures rise and after continuous rainy days turn clear.

(4) Lily leaf tip blight is a relatively common disease. It mainly damages leaf tips, and affected leaf tips turn blackish brown, necrotic or withered, and continually expand toward the leaf base. When the middle of the leaf is affected, spindle-shaped or oval spots form, with brown or reddish brown edges and a grayish white center, and many small black dots are scattered on the diseased part. The pathogen overwinters on diseased residues or diseased plants in the field, and in the second year spreads through wind and rain, invading through wounds or the epidermis, causing disease in the field. This disease begins in June. Plants with poor fertilizer and water management and weak growth are more susceptible.

(5) Lily blight, also known as lily foot rot. In years with a lot of rain, the disease is more severe, causing stems and leaves to rot and plants to lodge, affecting bulb yield. It mainly damages stems and leaves. On leaves, large water-soaked grayish green to brown spots appear, with no obvious margins. In severe cases, flowers and bulbs show water-soaked brown spots and rot, and in humid weather sparse white mold grows on the diseased parts. When stems and stem bases are affected, water-soaked brown wrinkled stripe-like spots appear at first and gradually expand upward and downward, causing stem rot and the plant to wither and collapse, and sometimes the stem tips of young leaves wither. The pathogen overwinters in the soil with diseased residue tissues, and in the second year, when conditions are suitable during the Spring Festival, it infects the host and causes disease. When there is a lot of rainfall and high air and soil humidity, the diseased parts produce large numbers of sporangia, which cause secondary infection through rain splash.