The symptoms are also known as powdery mildew and white back disease. Distributed in the country's planting mulberry district. Occurred in the lower part of the branches will be hardened or the back of the old leaves, the young leaves of the victims suffer lighter. In the early stage of disease, a round white powdery mildew spot appeared on the back of the leaf, and the contiguous enlargement was followed. The white powder was covered with the back of the leaf when it was serious. The chloasma was seen on the leaf surface and the lesion, and the small yellow particles appeared in the later white mold. Gradually turned yellow, eventually turned into black small particles, that is, pathogenic bacteria closed capsule shell.
The pathogen Phyllactinia morico-la (P. Henn.) Homma called the Sangsheng ball needle shell, belonging to the phylum Ascomycotina. Mycelia do not branch, criss-cross. The hyphae cling to the back of the leaves, sucked into the host cells to take in nutrients, leaf surface mycelia grow vertical conidiophores, colorless, with 3-4 diaphragm, the top of the enlarged component conidia. Conidia more than solitary, colorless, stick-like, size 608619 ~ 26 (um). In the later stage, the closed capsular fruit was formed, and the oblate spheroid was 183-283 um in diameter, with 5 to 18 acicular appendages in the periphery, sometimes as many as 32. Closed capsule: 9 to 14 ascospores. The ascus is colorless, round, with a short handle at the base, 60 to 10525 to 40 (um) in size, and 2 to 3 ascospores. Ascospores are colorless or light yellow, single cells, and oval in shape, and are 30-4919-26 (um) in size. In addition, it was reported that Uncinu-la mori Miyake described the mulberry silk shell as the pathogen.
Transmission routes and pathogenic conditions The pathogens overwinter in mulberry trunks or diseased leaves with closed capsules. When conditions are appropriate in the following year, the ascospore is dispersed, and it spreads to the mulberry leaf with wind and rain, resulting in white disease after 8 to 10 days of incubation. Spot, after a large number of conidia, re-infection, to the late autumn to form a closed shell overwintering. The optimum temperature for disease onset is 22 to 24°C, and the spores can germinate in the range of 30% to 100% relative humidity, and the relative humidity is 70% to 80%. When conditions are appropriate, the mature conidia germinate in 2 hours to form hyphae, and conidia are produced at 25°C for 72 hours. After a batch of conidia fall off, they form another batch every 3 to 5 hours. In low-temperature mountainous areas, mulberry gardens are more susceptible to diseases than in plain areas, with low groundwater levels, spring-cutting systems, excessive dense planting, or lack of potassium.
Control methods (1) The resistant cultivars selected for planting were generally resistant to disease when the mulberry cultivars were later hardened. Such as the lake mulberry 7, Husang 38, bent mulberry, flower mulberry, pear leaf mulberry, Xinjiang white mulberry and so on. (2) Clean mulberry garden. In the autumn and winter, the leaves of the ground are cleaned and the leaves are used for composting. (3) Reasonable leaf collection and dense planting of mulberry fields require multiple leaf collections. After summer harvest, we must apply sufficient summer fertilizer, pay attention to the application of potash fertilizer, and promote the application of special mulberry fertilizer. (4) Pharmaceutical control Baume 4 to 5 in winter. Lime sulfur or 50% sulfur rubber suspension 500 times spray trunk, branches. In the early stage of onset, spray 40% polysulfide suspension 800 times or 70% thiophanate-methyl wettable powder 1000 times, 50% thiophanate-methyl or 50% benomyl WP 1500 times, interval 10-15 Once a day, spray twice. Can be used 1% ~ 2% potassium sulfate or 5% polysulfide sprayed leaves, can inhibit the spread of the disease. In areas where resistance to the above fungicides has occurred, 40% DuPont Fuxing Emulsion 8000 can be used instead.
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