Control Methods for Powdery Mildew in Goji Berry Cultivation
[Symptom Characteristics] Mainly affects leaves. The leaf surface becomes covered with white mold patches (early stage) and powdery spots (later stage). These white mold patches and powdery spots are both the symptoms of this disease and the signs of this disease (the fungus's conidiophores and conidia). In severe cases, the goji berry plant appears entirely white, quite striking. Photosynthesis of diseased plants is blocked, ultimately causing leaves to gradually turn yellow and drop easily.
[Pathogen and Disease Characteristics] The pathogen is Oidium sp. of the Deuteromycetes (Fungi Imperfecti). In cold regions, the fungus overwinters in the soil as the sexual stage fruiting body (cleistothecium) along with diseased plant debris. In warm regions, the fungus mainly carries out primary and secondary infection through the asexual stage conidia, completing the annual disease cycle without a distinct overwintering period. Warm and humid weather or site conditions favor disease development. However, the fungal spores have drought-tolerant characteristics and can still germinate normally and cause infection under high-temperature and dry weather conditions.
[Control Methods] Spray fungicides early to prevent and control the disease. Like rust fungi, powdery mildew fungi are relatively sensitive to triazolone-type fungicides and to 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 ultra-fine sulfur suspension concentrate 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 intervals of about 7 days (colloidal sulfur, lime sulfur mixture, ultra-fine sulfur suspension concentrate) or 10 days (mancozeb) to more than 20 days (triadimefon), applied alternately, spraying evenly and thoroughly, to prevent and control the disease.