[ Objective] To find out the occurrence dynamic in alfalfa rust and powdery mildew in local alfalfa to set up the initial model between the final composite disease index and yield loss . [Method] The occurrence dynamic of the two diseases were surveyed by using the timing of sentinel surveying method. First, different disease level,were created, the chemical treatments were carried out on alfalfa fields.And then yield loss estimate model with a simple regression model were established after postpartum respectively . Finally , it was verified . [Result] Alfalfa rust is sporadic disease in the middle and first ten - day period of June, and rapid progression after the occurrence of disease. In the middle and last ten - day period of August, near maturity the disease index reached the highest,nearly 70.Alfalfa powdery mildew start in the middle ten - day period of July, and in August the progression is faster. And then near maturity disease index of alfalfa reach 55 or so. The model of relation between Y = 1. 671 6 x ＋ 1 . 605 8. between of the final composite disease index and yield loss. [ Conclusion]Rust and Powdery Mildew fail iU in mature and in the pod stage . The disease is rapid progress and the disease index was higher.As a result,They are heavier damage on alfajfa. It revealed positive correlation between the loss rate of alfalfa seed yield and the frnal composite condition of two diseases .%[目的]查明锈病与白粉病在当地种苜蓿上的发生动态,建立两病最终复合病情指数与产量损失率的关系模型.[方法]采用定时定点调查的方法,监测两病发生动态.对种苜蓿田进行药剂处理,造成不同病级,分别测产后用一元回归方法建立产量损失估计模型,并验证.[结果]种苜蓿锈病6月中上旬零星发病,且发病后病情进展较快,至8月中下旬种苜蓿近成熟期病情指数达到高点,接近70.种苜蓿白粉病始发于7月中旬,8月病情进展较快,至种苜蓿成熟期病情指数达到55左右.两病最终复合病情指数与产量损失率的关系模型为Y=1.671 6 X+1.605 8.[结论]种苜蓿锈病及白粉病发病于结束期与成熟期,且病情进展较快,病情指数较高,对种苜蓿危害较重.苜蓿种子产量损失率与锈病及白粉病两病最终复合病情呈正相关.
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