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There are three families of cycads, which are Cycadaceae, Stangeriaceae, and Zamiaceae. Among them, only 23 species in the genus of Cycas in Cycadaceae are mainly distributed in south China. In this paper, the main diseases of cycads and their damage to cycads were reviewed for the first time. Five cycad diseases have been reported only in China and Japan so far. Of those, cycad bulb rot disease (Fusarium solani [Mart.] App. et Woll.), cycad anthracnose (Colletotrichum sp.), cycad spot (Ascochyta cycadina Scalia) and cycad sooty blotch (Capnodium sp.) were reported in China, and cycad necrotic stunt virus (CNSV) was reported in Japan. Cycad bulb rot and cycad necrotic stunt virus lead cycad plants to death. Cycad anthracnose, cycad spot, and cycad sooty blotch are cycad leaf diseases that reduce cycad growth and their ornamental value. Because related plant pathogens Fusarium sp., Colletotrichum sp., Ascochyta sp., Capnodium sp. and cycad plants as potential hosts are common in subtropical and tropical areas, there will be high risk of cycad diseases in other countries due to cycad trade activities and expansion of the cultivation areas. Based on the existence of four key factors influencing cycad diseases, including hosts, pathogens, environmental conditions, and cultivation activities in each country, the potential cycad disease risk rank for each disease from the highest to the lowest level will be: cycad bulb rot > cycad spot > cycad anthracnose > cycad sooty blotch > cycad necrotic stunt virus. Risk prevention strategies for each disease are also discussed in this paper.
Keywords: cycad, cycad disease, disease risk analysis, cycle of infection, control