Monitoring methods of mulberry scale larvae, Pseudaulacaspis pentagona, were evaluated for determining the spraying time of effective chemical control. Among them, the calculation of the ratio of “more than half hatched egg batches” which was found to be suitable due to its accuracy, is however, time-consuming. Optimum spraying time is defined as the duration of the period required to achieve a ratio of more than half hatched eggs in egg batches (60 to 90%), which is referred to as “more than half hatched egg batches.” The use of sticky traps set inside a tea bush to capture crawlers of the mulberry scale is a simple and accurate monitoring method. The optimum spraying time occurs 2 to 5 days after the peak capture of the crawlers by the traps. The traps should be set up from the beginning of the egg hatching period, and should be examined daily or every other day to determine the peak capture of the crawlers. The use of sticky traps for monitoring is suitable for only the first generation of mulberry scale. Thus observations of “more than half hatched egg batches” are needed to determine the optimum spraying time for the second and third generations of the mulberry scale.