Loofah is a common fruit and vegetable vegetable that is delicious and nutritious. However, there is an unobtrusive phenomenon in the growth of loofah, that is, the loofah leaves are yellow. Why do loofah leaves turn yellow? How to prevent it?
What is the cause of yellowing of loofah leaves?
1. Yellow leaves caused by unreasonable fertilization. The data show that the ratio of demand for nitrogen, phosphorus and potassium in the growth of loofah is generally considered to be: 1.68:1:1.53. Due to the large-scale promotion of facility cultivation in recent years, the market is optimistic, the yield of loofah is increasing continuously, and the phenomenon of partial application of nitrogen fertilizer and potassium fertilizer is also common, especially in the period of flowering and melon, and potassium deficiency occurs more. The main symptoms are as follows: the leaf tip and leaf margin of the leaves are yellow, and then gradually spread to the mesophyll of the veins. In severe cases, the leaves are scorched and curled, and the fruit development is blocked. The deformed melons such as big head, thin waist and bent waist sometimes occur.
At the same time, excessive nitrogen fertilizer, especially ammonium nitrogen, will directly affect the absorption of calcium fertilizer by loofah and produce calcium deficiency. The main manifestations are: the growth of new leaves is blocked, the leaf margin is incomplete, the leaves are shrunk, and there are yellow or yellow-brown plaques. The yellow leaf phenomenon reflected by netizens should be related to the reasons for these aspects.
2. Small yellow spots on the old leaves caused by brown spot disease. The loofah brown spot is mainly harmful to the leaves. The lesions are round, long or irregular, brown to taupe, 0.5-13 mm in diameter, with obvious or inconspicuous edge of the lesion, and a chlorotic to yellow halo. Less common. The disease is called the genus Cercospora, the fungus of the fungus. The pathogens overwinter on the pathogens of the mycelium or conidia in the soil. In the spring of next year, the conidia are used for initial infection and reinfection, and spread by airflow. Warm and humid, partial application of nitrogen fertilizer, continuous cropping and other conditions are likely to cause serious disease.
How to do loofah leaves yellow
1. Implement non-melon vegetables for more than 2-3 years of rotation, apply fully fermented and decomposed organic fertilizer, formulate fertilization according to the demand ratio of nitrogen, phosphorus and potassium in loofah growth, and increase the application of calcium nitrate and borax per mu. - 2 kg to enhance the disease resistance of plants.
2. Chemical spray control:
(1) 80% pyraclostrobin-mycin wettable powder 750 times liquid + 60% calorie calcium 750 times liquid + 21% calorie boron 750 times liquid.
(2) 41.4% benzofuric acid ester 1 +1 combination (25 ml of water + 10 g of powder) 428 times liquid + 10% high boron active potassium calcium water 300 times solution.
(3) 25% azoxystrobin suspension 1500 times solution + 60% azole ether · Desen water dispersion granules 750 times solution + 10% very zinc calcium boron powder 300 times solution.
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