Symptoms and control methods of lily blight

Symptoms: This disease mostly occurs on the young leaves of plants, and stems and flowers can also be affected. In the early stage of the disease, oily spots appear on infected leaves, which gradually expand and turn grayish green. In severe cases, the leaves and flowers become soft-rotted. On infected stems near the ground, the diseased part is water-soaked, turns brown, and shrinks, and the plant wilts, lodges, and dies. If the bulb is infected when it sprouts, only the top of the young stem withers. When humid, white mold grows on the diseased part.

Pathogen: The pathogens are Phytophthora cactorum (Leb. et Cohn) Schrot. and Phytophthora parasitica Dast., both belonging to the fungi of Mastigomycotina, Oomycetes, Peronosporales, Phytophthora.

Disease pattern: The two Phytophthora species mainly overwinter as oospores on diseased residues in the soil. When conditions are suitable the following year, the oospores germinate and produce germ tubes that invade the plant, after which sporangia and zoospores are produced on the plant for secondary infection. Under rainy conditions, poor drainage, and low-lying, humid conditions, the disease is severe.

Control: ① Reduce sources of infection: pull out diseased plants and burn them in a centralized manner. ② Strengthen cultivation management: for large-scale production areas, dikesone can be used to irrigate the soil, and for potted plants, disinfected soil should be used to fill the pots. The planting site should have good drainage, and flat land can be cultivated in raised beds. Avoid damaging the stem base during horticultural operations. ③ Chemical control: during the plant growth period, Bordeaux mixture and other fungicides can be sprayed.