Brown spot disease is also a widespread disease on garden plants that occurs frequently in the crape myrtle growing season. When the brown leaf spot of Lagerstroemia crassipes is serious, it often leads to a large number of yellow leaves and shedding of plant leaves. Affects the viewing and flowering.
First, performance symptoms
The pathogen of Lagerstroemia brown spot is a fungus that mainly invades the leaves, and usually the lower leaves begin to develop and spread gradually upwards. In the early stages of the disease, the lesions are of circular or nearly circular shapes, with a few irregular shapes. The lesions were purple-black to black, and the edges were lighter in color. The color of the lesions was then deepened, showing black or dark black, and the boundary between healthy and healthy parts was obvious. The color of the lesions in the center of the lesions has faded and the gray and black mold spots have appeared. When the disease is severe, the lesions are connected and the entire leaf quickly turns yellow and falls off prematurely.
Second, the law of occurrence
The infestation of Lagerstroemia brown spot is caused by the infection of C. littoralis. The pathogenic bacteria is wintered on the diseased body in the form of mycelium or conidia, and the initial infection and re-invasion are carried out by the conidia the following year. Dyed and spread by air currents or wind and rain. Brown spot disease in Tianshui area generally begins to occur in early summer and is seriously endangered in autumn. It is easy to break out in high temperature and rainy weather, especially in the year or season when the storm is frequent; usually the lower leaves are more susceptible than the layers of leaves.
Third, control methods
1, early detection of horticultural control, timely removal of diseased branches, diseased leaves, and concentrated burned or buried in order to reduce the source of bacteria. Strengthen cultivation management, pruning, and make plants airy and transparent. Potted crape myrtle is best to replace new soil every year.
2. Chemical control
In the early stage of the onset of brown spot, Lactobacillus sp. can be sprayed with 800-1000 times of bacteria, 50% of carbendazim WP 500 times, or 65% of dexamethasone WP 1000 times, or 75% of chlorella. Clear WP 800 times solution. In the severe period of the brown leaf spot of Lagerstroemia speciosa, spraying with 2000-3000 times of spray chlorella or Amisidae can be used.
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