Disease knowledge of Leaf spot of Rhododendron
Round spot, or irregular polygonal spot, dark brown, 1mm-5mm in diameter. In the later stage, the central tissue of the lesion turned gray. When the disease is serious, the disease spots are connected to each other, resulting in withered and yellow leaves and early fall. Under the moist environment, there are many brown mildew spots under the leaf spot, that is, the conidia and conidiophores of the pathogenic bacteria.
Pathogen and disease status: Cercospora CercosporarhocdodendriFer., Trichospora, Cercospora, Cercospora. The pathogen overwintered on the plant remains and formed conidia in the following year as the source of primary infection. The conidia are transmitted by wind and rain and invade from the wound. In Jiangxi, the disease began to occur in mid-May and reached its peak in August. In Guangzhou, the peak of the disease is from April to July, and the rhododendron cultivated in greenhouse can cause the disease every year. More Rain Water, more fog and heavy dew are conducive to the disease, because conidia can germinate only in water droplets. Poor ventilation and light transmission and poor plant growth can aggravate the occurrence of diseases. Prevention and control measures:
1. The fallen leaves were thoroughly removed and treated in autumn, and the diseased leaves were removed in time during the growing season.
2. The planting density of potted flowers is suitable in order to ventilate and penetrate light and reduce the humidity of leaves. In summer, potted flowers are placed in an outdoor shade to reduce wounds caused by sunburn and mechanical damage.
3. Immediately after enlightening, spray 65% Dyson zinc wettable powder 500Mel 600x liquid, or 50% carbendazim wettable powder 500Mel 800x liquid, or 70% methyl topiramate wettable powder 1000 times liquid. Spray once every 10-14 days for 3 times in a row.
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Control techniques of Leaf Blight of Rhododendron
First, the main symptoms: occur in the leaves, mostly in the tip of the leaves. In the initial stage, the disease spot is faded green macula, the disease spot spreads inward from the edge, showing an irregular shape; in the later stage, the disease spot is yellowish brown, and when the disease leaf is serious, the disease leaf is dry. Second, the cause of the disease: fungal diseases. The pathogen lives on the plant disease residue and spreads through watering, insects and human activities. It can occur all the year round in the indoor environment. High temperature, dryness and poor ventilation are easy to cause diseases. Plant growth is weak or affected by insect pests (especially aphids, shell insects, whitefly)
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Rhododendron culture
Azaleas are very beautiful, and everyone is willing to raise them, but how can they raise them well? There are many fastidious here, azaleas like acidic soil and water, afraid of alkaline soil and water, afraid of waterlogging: like warm and cool, afraid of dry and hot environment, afraid of dry air; like semi-overcast, afraid of scorching sun; like thin fertilizer, afraid of thick fertilizer. What kind of soil larch humus soil acidity is suitable, soil quality is loose, fertile, good permeability, suitable for rhododendron growth. What kind of water should be used for cuckoos? the PH value is less than 7. In areas where the water quality tends to be alkaline, in addition to storing Rain Water and snow water, acidified water can be added to 100 jin of water.
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