什么叫植物病害，植物病害一般是指在植物生长、发育、贮藏、运输的过程中个受到外界不良环境因素的影响或有害生物的侵染，使其在生理和形态上发生了系列的变化，而使植物的经济价值受到影响。这种变化，即称为病害。
What is plant disease? It generally refers to the infection the plant in the process of growth, development, storage and tranportation due to bad environmental influences or deleterious vermins,which causes a series of physiological and morphological changes that results the influence to the plants' economic value.This kind of change is called disease.
这种变化不是机械的，而要经过由生理变化到形态变化的全部过程。因此，植物病害往往不是从—开始就能见到的。只是在其—定的阶段能见到。此外，植物的病受，必须影响到植物的经济价值，对人类有不利的影响，才能称之为病害。
It's the whole process of physiological change as well as morphological change more than a simple process.Therefore, it couldn't be noticed at the beginning.It could only be discovered at a particular stage. Besides only when the disease influences the economic value and infect human's health could we call it plant disease.
例如有些寄生物可使花卉表现美丽多姿；有些茵类寄生后增加丁某种蔬菜的可食性；这些病变均不属于病害之列。掌握住以上原则才能对植物病害有—个完整的概念。
For example, some parasite makes the flowers more beautiful ; some viruses makes the vegetables more edible. Neither of them could be ranked as disease.Only when the principles are mastered can we have a full recognization of plant disease.
病害的发生．一般包含了寄主植物，病原物在一定环境条件下互相斗争的复杂过程。当环境行利于；植物而不利于病原物时，植物不发生病害；而当环境不利于植物，而有利于病原物时，植物病害才能形成。
Plant suffering from disease is a complex process of pathogenic struggling against each other under certain conditions.When the environment is favorable to the plant rather than the pathogenic, the plant can't be infected. While the environment is favorable to the pathogenic rather than the plant, plant disease will take place.
因此，有时在生产中遇到病害问题．不易判定谁是真正的病原。关键在于，只有能决定病害特点与性质的因素(包括生物的和非生物的因素)才是真正的病原。
Therefore,it's hard to determine the real pathogenic when we encounter disease problem in the production process. Disease whose character and factor could be recognized are true pathogenic.
(专业词语翻译未必准备，仅供参考)
