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How to Control Impatiens Leaf Spot Disease

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I. Symptoms of Damage: Disease scientific name: Phyllosticta impatientis Fautr. Impatiens leaf spot disease mainly damages the leaves. Initially, small yellow spots appear, gradually expanding outward into circular lesions, 2-5mm in size. Later, the center of the lesion turns light brown or grayish-white, with slightly raised brown edges, and black small granules form on the surface, which are the pathogen's pycnidia. If the pathogen invades from the leaf tip or leaf margin, it causes the leaf tip to die and the leaf margin to scorch. The disease occurs in Guangdong and Yunnan from July to September. II. Morphological Characteristics of the Pathogen: The pathogen is called

I. Symptoms of Damage: Disease scientific name: Phyllosticta impatientis Fautr. Impatiens leaf spot disease mainly damages the leaves. Initially, small yellow spots appear, gradually expanding outward into circular lesions, 2-5mm in size. Later, the center of the lesion turns light brown or grayish-white, with slightly raised brown edges, and black small granules form on the surface, which are the pathogen's pycnidia. If the pathogen invades from the leaf tip or leaf margin, it causes the leaf tip to die and the leaf margin to scorch. The disease occurs in Guangdong and Yunnan from July to September.

II. Morphological Characteristics of the Pathogen: The pathogen is called Phyllosticta impatientis, belonging to the fungi imperfecti. Pycnidia are scattered on the leaf surface, spherical to nearly spherical, 82-102um in size. Conidia are ovoid, single-celled, colorless, containing 1-2 oil droplets, 3.0-5.0 X 2.0-3.0 (um) in size.

III. Disease Characteristics: The pathogen overwinters as pycnidia on diseased plant debris. When conditions are suitable the following year, conidia are produced and spread by air currents and rain, causing primary infection and re-infection.

IV. Control Methods

(1) Remove diseased fallen leaves promptly.

(2) When necessary, spray 40% chlorothalonil suspension concentrate at 500 times dilution, or 80% mancozeb wettable powder at 600 times dilution, or 70% mancozeb wettable powder at 500 times dilution.

V. Commonly Used Fungicides: 70% mancozeb wettable powder, 40% chlorothalonil suspension concentrate

VI. Latest Special-Effect Fungicides: mancozeb, azoxystrobin, kresoxim-methyl, etc.

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