| Abstract: In order to find out the influence of external factors on blight of Gynostemma pentaphyllum, and provide basis for effective control, in the main planting areas of Gynostemma pentaphyllum in Chengguan town and Chang'an town of Pingli county, 5 sites were selected to test the occurrence of blight of Gynostemma pentaphyllum under different conditions, such as different altitudes, soil pH values, previous crops, fertilizer types and varieties of Gynostemma pentaphyllum. The results showed that the occurrence of blight of Gynostemma pentaphyllum was closely related to the growth environment and cultivation conditions. The disease index decreased by about 10 for every increase of pH value. The occurrence of blight was both severely affected by the previous crops and intercropping crops. Potato was the most important factor, tomato was the second, and pepper was the third. The occurrence of blight was relatively light when intercropping or previous crop was corn. For every 100 m elevation of altitude, the disease index of blight decreased by 6.4. The disease of Gynostemma pentaphyllum was earlier and heavier when urea was applied excessively in the planting process. The disease was later and heavier by using diammonium phosphate + urea, the disease was lighter by using farmyard manure + biogas slurry, and the disease was the lightest and later by using rapeseed cake + biogas slurry. The factors influencing the occurrence of blight were found out. Firstly, the single use of chemical fertilizer was the key factor to the occurrence of the disease, secondly, the previous crop, and thirdly, the low altitude and low pH value. |