Symptoms have occurred from Liaoning in the north to Taiwan and Yunnan in the south. The main damage to the leaves occurs mostly on the back of older mulberry leaves, rarely seen on young leaves. Primary small pulverized coal black spots, with the spread of the disease, also produce the same size of grayish yellow to dark brown discoloration spots on the corresponding leaf surface. 4 When the lesions are severe, the lesions fuse or cover the leaves and back, resulting in discoloration of the entire leaf. The disease often occurs in combination with powdery mildew and forms black and white mixed spots on the back of the leaves.
Pathogen Sirosporium mori (H. & P. ​​Syb.) M. B. Ellis=Clasterosporium mori H. & P.Syd. The hyphae cling to the back of the leaf, the sucker attached to the leaf surface, and the hyphae invade the leaf tissue from the stomata to absorb nutrients. Conidiophore brown, mostly growing from or on stolons, erect or tufted, cylindrical, 33-564-6(um), with several small projections on top and mostly septum near base Two to three; conidia are produced on each small bulge, and some produce conidia directly from the hyphae. The conidia are brown in color and have different shapes. The base is large and the ends are fine. There are rod-shaped rods on the conidiophores. There are also cylinders. The rods have 2-7 membranes and the size is 25-374-6. (um); The bases on the hyphae are fine, the ends are thick, stick-shaped, with 4-7 membranes, size 45-653-5.5 (um).
Transmission routes and disease conditions The disease is mainly caused by hyphae or conidia on the diseased leaf tissue overwintering, in the summer and autumn of the following year, it produces conidia on the wintering hyphae, spread by wind and rain, causing initial infection, after the new lesions On the other hand, conidia were produced and reinfested. The incubation period is about 26 days. It takes about 2 hours from initial infection to re-infection. The disease mostly occurred before the late autumn defoliation. The early cultivars of the mulberry stalks were susceptible to disease, poor ventilation and light transmission, and severe drought in summer and autumn.
Control methods (1) Selection of varieties of anti-fouling leaf diseases such as Husang 28,29,38,39. (2) Before the leaves fall in the late autumn, remove residual leaves from the mulberry tree for feed or manure, reducing the source of bacteria in the next year. (3) During the rearing of the silkworm, the lower leaves of the shoots are collected first to prevent the onset of leaf aging. (4) Strengthen fertilizer management. Appropriately increase fertilization material after summer harvest, timely irrigation in drought in autumn, so that mulberry leaves are tender. (5) Spray 70% mancozeb WP 500 times or 65% zeocin WP 600 times, 65% TB wettable powder 1000 times, 50% polymyxin wettable Powder 800 times liquid.
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