The mulberry for production of mulberry fruit, found the damage and quantity according to the level of damage by the A. mori, and through regression analysis, we set up a economic injury level. The level of damage by A. mori was to be artificially adjusted, for 2 percent, 5%, 8 percent, and 11 percent of leaf damage. Investigate, From May 31 to June 14, they compared the damage to each damage level and the growth and development and quantity. The survey found that the more damage level, the more severe the damage. The ratio of damage fruit was 5.1 percent, 11 percent, 13.2 percent, 23.9 percent, respectively. And the quantity was reduced by about 33% from 11 percent to 2,387 g/tree compared to the 2 percent to 3,557 g/tree. There's no difference in the damage caused by the sclerotium disease, and the growth and development, such as the length of the tree, the length of the branches, and the thickness of branches. The relationship between the damage level and the ratio of damage fruit was able to obtain relations with the linear regression, Y = 2.129552 X +0.569663(R2 = 0.98). It's the result of an analysis, which analyzed the damage level's relationship with the ratio of damage fruit have a high correlation rate. Therefore, It’s about the ratio of the quantity losses is 5 percent, the ratio of damage leaf is 2.08 percent. If the ratio of damage leaf is more than 2.08 percent, the damage will be required the control. It is judged.