Mulberry bacterial disease

Symptoms are also known as bacterial black fungus, leaf shrinking bacterial disease, bad head disease and so on. Distributed in the country's planting mulberry district. The main damage is new shoots and young leaves, causing brown spots or rot in the leaves, curling up, withering of the terminal buds or blackening of new shoots, resulting in a 20% reduction in yield. There are two kinds of black and dry leaf types. Black dry type often produces different types of symptoms due to different sites of infection. The pathogens invaded by leaf stomata caused punctate yellow-brown spots, and the surrounding leaves were slightly whitish; the bacteria invaded the vascular bundle from the wounds at the petiole or leaf veins, irregular polygonal spots appeared on the leaves, and the initial oil stains were yellow-brown afterwards. The merging into one piece causes the leaves to turn yellow or fall off; when the bacteria invade from the leaf tip, the young leaves or young shoots turn black and rot and become rot-shaped, and when the humidity is high, the diseased part overflows with pale yellow bacteria and pus; the bacteria from the shoots The epidermis invades, the diseased part uplifts, and is present with long strips or spindles, with more in the upper part. When the bacteria invades from the phloem to the xylem or pith, the strips appearing are mostly brown. The leaves of the diseased leaf were brown and near-circular, with perforation of the posterior disease, browning of the leaf margins, leaf rot or chlorosis of the surrounding tissues; lesions of the leaf veins, the diseased leaf curled to the back and shrank like a leaf, and was severely shedding. Shoot disease is a cracked shuttle-shaped black spot, and the top buds are withered and darkened. Under the conditions of high temperature and high humidity, the above two types of diseased bodies overflowed with a pale yellow adherent, “spill pus”. After drying, the pyodesia condenses into shiny beads or assumes a pellicle.

Pathogen Pseudomonas syringae pv. Mori (Boyer et Lambert) Young et al. Pseudomonas syringae mulberry induced disease, is a bacterium. The cells were short rods, 1.43.2 (um) in size, blunt at both ends, with 1-10 flagellates, no pellicles, no spores, and Gram negative staining. On broth agar medium, the colonies were milky white, translucent, round, raised in the middle, and the edges were more neat. Growth temperature limit of 2 - 35 °C, growth temperature 25-30 °C. Lethal heat temperature 48 °C, 10 minutes, dry heat 90 °C lethal, to adapt to pH 5-9, the optimum pH 6.3-8.0.

Transmission routes and pathogenic conditions The pathogens overwinter in mulberry branches and winter buds. It has been reported that wintering can also occur on rotted branches in soil. The pathogenic bacteria of Hunchun produced a large number of pathogens, which invaded the newly emerged buds and leaves, resulting in the onset of buds, which became the source of early infection in early spring. When the humidity is appropriate, the disease overflows bacteria and pus, and it is transmitted to the young shoots or young leaves after contact with wind and rain, insects, foliage, etc., and re-infected from the wound or stomata. Sick saplings and scions are spread long distances. In hot and humid seasons, stormy seasons, sudden rise in temperature or insect pests, and frequent wounds. Low-lying terrain, high groundwater level, and heavy application of nitrogenous fertilizers are serious. White skin fire mulberry, hairy leaf species, Tongxiang green, Yannong 55, Huang Lutou, Husang 7 susceptible.

Prevention methods (1) Selection of Husang No. 13, Husang 199, 6301, 580l, Fengcheng No. 1, Nongsang No. 8, Nongsang No. 18, Yuyu No. 2, Yuyu 151, No. 1 No., Pear Leaf Sang, Large Sangyu No.2, Heilusan and other disease-resistant varieties. (2) Winter cutting tip, spring disease buds, diseased branches, reduce the source of bacteria. (3) When grafting, the scion shall be strictly selected and the diseased scions shall be removed in a timely manner. The diseased seedlings shall be excavated in time when they are found, and sprayed with 0.7% Bordeaux mixture or 14% colubrid ammonia solution for 300 times. (4) In the early stage of onset, the young shoots are sprayed with 500-500 times of oxytetracycline 300-500mg/kg or streptomycin 100mg/kg or 15% streptomycin and 1.5% oxytetracycline. 10 times a day, continuous 3-4 times can control the disease spread, such as with 0.1% copper ammonia solution (50g copper sulfate plus 12% ammonia 500m1, water 50kg) every 2 days; once even against 2 times Good preventive effect. (5) spraying 50% carbendazim WP or 50% thiophanate-methyl wettable powder 1000 times, and then 500 times the root can also inhibit the expansion of the disease.

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