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What are the control methods for powdery mildew in goji berry (Lycium barbarum)?

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[Symptom characteristics] It mainly damages the leaves. The leaf surface is covered with white mildew spots (early stage) and powdery patches (slightly later). These white mildew spots and powdery patches are both the symptoms of this disease and the signs of this disease (the pathogen's conidiophores and conidia). In severe cases, the goji berry plant appears entirely white on the outside, which is quite striking. Photosynthesis of the diseased plant is hindered, ultimately causing the leaves to gradually turn yellow and fall off easily. [Pathogen and disease occurrence characteristics] The pathogen is Oidium sp. of the Moniliaceae in the Deuteromycotina. In cold regions, the pathogen overwinters in the soil with diseased debris as the sexual-stage fruiting body, the cleistothecium.

[Symptom characteristics] It mainly damages the leaves. The leaf surface is covered with white mildew spots (early stage) and powdery patches (slightly later). These white mildew spots and powdery patches are both the symptoms of this disease and the signs of this disease (the pathogen's conidiophores and conidia). In severe cases, the goji berry plant appears entirely white on the outside, which is quite striking. Photosynthesis of the diseased plant is hindered, ultimately causing the leaves to gradually turn yellow and fall off easily.

[Pathogen and disease occurrence characteristics] The pathogen is Oidium sp. of the Moniliaceae in the Deuteromycotina. In cold regions, the pathogen overwinters in the soil with diseased debris as the sexual-stage fruiting body, the cleistothecium. In warm regions, the pathogen mainly carries out primary infection and reinfection through asexual-stage conidia, completing the year-round disease cycle, with no obvious overwintering period. Warm and humid weather or planting site environment favors disease occurrence. However, the pathogen spores have drought-tolerant characteristics, and under high-temperature and dry weather conditions, they can still germinate normally, infect, and cause disease.

[Control methods] Spray pesticides early to prevent and control the disease. Like rust fungi, powdery mildew fungi are relatively sensitive to triazolone fungicides as well as organic or inorganic sulfur fungicides. Before disease onset, or at the latest after disease is observed, continuously spray 45% lime sulfur mixture crystals or paste at 300 times dilution, or 50% colloidal sulfur or ultramicro sulfur suspension at 200-400 times dilution, or 15% triadimefon wettable powder at 2000 times dilution, or 70% mancozeb at 600 times dilution, 2-3 times, with an interval of about 7 days (colloidal sulfur, lime sulfur mixture, ultramicro sulfur suspension) or 10 days (mancozeb) to more than 20 days (triadimefon) per spray, applied alternately, sprayed evenly and thoroughly, to prevent and control the disease.

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