Method for identifying alfalfa brown spot

The invention discloses a method for identifying alfalfa brown spot. The method comprises the following steps: separating pathogens to be placed on a PDA culture medium platform to be cultured, washing with sterilized water, and filtering to obtain a spore suspending liquid; taking leaves of alfalfa, removing leafstalks, washing, conducting sterilization treatment, chopping into small blocks, putting into a 0.3% water agar culture medium containing 50 [mu]m/mL benzimidazole, and culturing for 4 days; selecting good leaves with the normal growth state, tiling on the culture medium, lightly stabbing the leaf surfaces with a pin, dripping the obtained spore suspending liquid at the stabbed parts, and conducting inoculation at the condition that the relative humidity is almost 100%, the temperature is 20 DEG C, and illumination is not provided, for 20 h; after the inoculation is finished, transferring the leaves into a growth box for culture, alternating the light intensity of 9000 lux and darkness every 12 hours, and observing and recording the infection and disease development condition every day. Through the reasonable culture and inoculation method and a reasonable culture medium formula, the identifying efficiency is improved, and large-batch screening is facilitated.