四、桑树侵染性病害的发生发展桑树侵染性病害的发生,是桑树在一定的环境条件下,因受到病原生物的寄生而引起的,并经进一步的发展而使病害蔓延和流行。 (一) 病原物的寄生性和致病性 1.寄生性:寄生性是指病原生物依赖寄主植物获得营养物质而得以生存的能力。这种病原胸称为寄生物。寄生物对寄主植钩为寄生性可分为专性寄生和非专性寄J生两种:. 1。专牲寄生:寄生物只能从活的寄主细胞和组织中获得养分,.当植物的.细 Fourth, the occurrence of mulberry invasive disease Mulberry invasive disease occurs, mulberry under certain environmental conditions, due to the parasites caused by the pathogen, and by the further development of disease spread and epidemic. (A) pathogen parasitism and pathogenic 1. Parasitic: parasitic refers to the ability of pathogenic organisms to rely on host plants to obtain nutrients to survive. This pathogen is called a parasite. Parasites for the host plant hook for the parasitic can be divided into two types of parasitic and non-specific sent J :. Special parasitic parasites: parasites can only obtain nutrients from living host cells and tissues,