Symptom Identification and Control Methods of Lily Blight
Blight is an important disease of lilies, widely distributed, occurring mostly in the south, with occasional outbreaks in protected cultivation in the north. Usually 5%-10% of plants are diseased, affecting lily production to a certain extent; in severe cases it can reach over 30%, causing plants to die in patches and significantly affecting lily yield and quality.
Symptoms: This disease can infect all parts of the lily. When the stem is infected, it initially shows water-soaked light brown to greenish-brown rot, gradually spreading upward and downward, causing the plant to wither and die or topple. When leaves are infected, small water-soaked spots initially appear, later developing into grayish-green to dark green large spots, ultimately causing the diseased leaves to rot or wither. After flower organs are infected, they show yellowish-brown to dark brown soft rot; in humid air, a sparse white mold layer forms on the surface of the diseased tissue, which is the pathogen's sporangiophores and sporangia. When the bulb is infected, it initially shows water-soaked yellowish-brown necrotic spots, which later expand and rot, producing sparse white mold on the surface of the diseased tissue.
Pathogen: Phytophthora cactorum (Leb. et Cohn) Schrotr, belonging to the flagellate fungi, a Phytophthora fungus. The pathogen's hyphae are sparsely branched, 2-6 micrometers wide; sporangia are oval to nearly spherical, measuring 33.5-41 micrometers x 28-34 micrometers. Oospores are spherical, with a diameter of 27-33.5 micrometers.
Disease development pattern: The pathogen overwinters in the soil as chlamydospores or oospores remaining in diseased plant debris. When conditions are suitable, chlamydospores or oospores germinate and invade the host, causing disease; the diseased areas produce large numbers of sporangia, which after germination release zoospores or germinate directly to cause secondary infection. Temperatures of 26-28°C and humid or rainy weather are favorable for disease development. Poor drainage after rain and dense, tender plants in the field favor the occurrence and development of the disease.
Control methods
1. Adopt high-ridge or high-bed cultivation, prepare the soil finely, and build field drainage ditches properly so that water can be drained promptly after rain.
2. Plant at a reasonable density, apply fully decomposed organic fertilizer, and appropriately increase potassium fertilizer to enhance plant disease resistance.
3. Strengthen field management; when diseased plants are found, dig them out early and bury them deeply in a centralized place outside the field. After disease onset, appropriately reduce watering.
4. Apply pesticides promptly in the early stage of disease; in protected cultivation, dust application techniques are best used.