Orchard disease of mango: bituminous coal disease

The disease is distributed in Yunnan, Guangxi, Hainan, Guangdong and Fujian provinces (autonomous regions). It is a frequent and major disease and is common in arid areas. Leaf damage can reduce the photosynthetic efficiency of crown, affect the growth of branches and leaves, cause crown weakness, hinder pollination and fertilization of flowering spike, reduce fruit setting rate and fruit appearance quality. The leaves affected by symptoms are covered with a loose, reticulate black powder layer, which hinders leaf photosynthesis. Mildew is limited to the leaf surface, and the combination with the leaf is not close and easy to erase. During the florescence, the black mold layer covered the inflorescence, spike and lateral floret, which affected the pollination of the flower ear, resulting in a decrease in fruit setting rate; the small fruit was easy to fall off due to the influence of the mold layer, and the affected fruit had dirty pericarp, poor appearance and easy to induce postharvest diseases in the later stage of fruit growth. There are two kinds of common pathogens: Capnodium mangiferae. The disease caused by Cladosporium [Cladosporiumherbarum (Pers.) Lk.ExFr.] Causing tobacco mildew, both of which are called bituminous coal disease. The primary infection source of the disease comes from branches and old leaves, and the pathogen can reproduce all the year round in southern Guangdong and Hainan provinces. the degree of the disease is related to the population density of honeydew-secreting insects and meteorological factors. In areas with obvious spring drought (western Hainan, Leizhou Peninsula in Guangdong, Baise in Guangxi, Yunnan) or drought years in fruiting period, Homoptera (flat-beaked leafhopper, aphids, shell insects, white moth wax cicada, etc.), Thysanoptera (thrips) and mites have high population density and are rampant, sucking young leaves and young fruit juices, while excreting a large amount of amino acids, sugars and waxes adhering to the surface of the host tissue. These feces are a good substrate for the reproduction of soot bacteria, and the mycelium propagates rapidly to form a large amount of black mold layer covering the surface of branches, leaves and fruits. The disease occurred more seriously in orchards with old trees, shade and poor cultivation management. The control method ① should strengthen the orchard cultivation management, prune reasonably, the old orchard should retract the crown, cut off the inner chamber branch, withered branch and disease and pest branch, improve the ventilation and transmittance of the orchard, and reduce the hidden places of leafhopper, aphid, thrips and mites. ② regularly controls leafhoppers, aphids, thrips and mites in the dry season. ③ regularly apply fungicides to inhibit mold growth, using 75% chlorothalonil wettable powder 800-1000 times or 40% methomyl glue suspension 600-800 times, spray tree crown, application interval of 15-20 days, can be applied continuously for 2-3 times.