Abstract: The scale insect Stotzia sp.is an important pest of plum Prunus salicina.The insect has one generation annually in Kunming district,and overwinters by second instar nymphs on plum branches.Each female can lay 600 eggs in average.The nymph has 2 instars,the first instar nymphs feed on leaves,and the second instar ones feed and fix on 1-2 years old branches until they become adults.The adult period and the active period of the first instar nymph are the important times for eliminating the pest.The most effective methods to lower the population are cutting away twigs which bear the female adults from late February to middle March and spraying 1:3000 deltamethrim liquor to kill the active first instar nymphs from late April to late May when the pest is densely populated.The defective management of the plum orchard is the chief reason for causing outbreak.The feasible measures to control the pest are improving management methods of the orchard,eastablishing the pest population monitering system,protecting natural enemies,and applying necessary chemical pesticides.