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How to control powdery mildew on the medicinal plant honeysuckle (Japanese honeysuckle)?

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Honeysuckle, scientific name Lonicera japonica Thunb., also known as mountain honeysuckle. It belongs to the Caprifoliaceae family and is a perennial vine-like shrub. The buds or nearly opened flowers are used as medicine. The leaves and branches can also be used as medicine. It has the effect of clearing heat and detoxifying. Starting in the 1960s, it was converted from wild to cultivated, and now from south to north, many cities and counties grow it, and at one time the area was quite large. The symptoms mainly damage the leaves, and sometimes also damage the stems and flowers. The lesions on the leaves are initially small white spots, then expand into white powdery patches, and in the later stage the entire leaf is covered with a powdery layer, and in severe cases

Honeysuckle, scientific name Lonicera japonica Thunb., also known as mountain honeysuckle. It belongs to the Caprifoliaceae family and is a perennial vine-like shrub. The buds or nearly opened flowers are used as medicine. The leaves and branches can also be used as medicine. It has the effect of clearing heat and detoxifying. Starting in the 1960s, it was converted from wild to cultivated, and now from south to north, many cities and counties grow it, and at one time the area was quite large.

The symptoms mainly damage the leaves, and sometimes also damage the stems and flowers. The lesions on the leaves are initially small white spots, then expand into white powdery patches, and in the later stage the entire leaf is covered with a powdery layer; in severe cases the leaves turn yellow and become deformed or even fall off; the lesions on the stems are brown, irregular in shape, and covered with white powder; the flowers become twisted and in severe cases fall off.

The pathogen Microsphaera lonicerae (Dc.) Wint. in Rabenh. is called honeysuckle powdery mildew, belonging to the Ascomycota fungi. The ascocarps are scattered, spherical, dark brown, 65-100 μm in size; 5-15 appendages, 55-140 μm long, 0.7-2.1 times the diameter of the ascocarp, colorless, without septa or with 1 septum, 3-5 times dichotomously branched. Asci 3-7, oval to elliptical, 34-58 × 29-49 (μm). Ascospores 2-5, elliptical, 16.3-25 × 8.8-16.3 (μm). The asexual state is Oidium sp. mycelium, epiphytic on both leaf surfaces, conidiophores erect, 50-94 × 7-10 (μm); conidia 2-3 in chains, a few solitary, elliptical, cylindrical, produced in a basipetal manner, 28-49 × 12-20 (μm).

Transmission routes and disease conditions: The pathogen overwinters as ascocarps on diseased residues, and the following year the ascocarps release ascospores for primary infection. After the disease occurs, conidia are produced on the diseased parts for secondary infection. Warm, dry conditions or shaded spaces between plants make the disease more likely to occur. Excessive application of nitrogen fertilizer and alternating dry and wet conditions make the disease severe.

Control methods (1) Select disease-resistant varieties, pay attention to pruning, and increase ventilation and light penetration. (2) In the early stage of the disease, spray 50% colloidal sulfur 100 g mixed with 20 kg water or 15% triadimefon wettable powder at 2000 times dilution.

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