Arrowhead scale, Unaspis yanonensis, is a serious scale insect pest of citrus in Jeju. The sticky taping of 1.0 cm diameter twig was a good survey method for arrowhead scale crawler. There are three times crawler occurrence season - late May to early July, late July to middle September and late September to late October. But the third occurred crawlers are all died during overwintering in open-field groves. This study was conducted to provide information on efficient sampling plan for arrowhead scale within the tree. Twig and fruit was fit for secondary sample unit by two-stage variance analysis. Both sample number per tree (primary sample unit) was eight twigs or fruits. Taylor’s power law was better described the distribution characteristic of arrowhead scale than Iwao’s patchiness regression. The slope of both linear regressions was greater than “1” which means aggregative distribution pattern. Minimum sample size to estimate the density was calculated using by two parameters of Taylor’s power law. To estimate the mean density on twig and fruit by binomial sampling plan, the optimum tally threshold was 5 and 7, respectively.

• Jeong Heub Song(Research Team for Sustainable Agriculture, Jeju Agricultural Research & Extension Services)
• Soon Yeong Hong(Research Team for Sustainable Agriculture, Jeju Agricultural Research & Extension Services)
• Shin Chan Lee(Research Team for Sustainable Agriculture, Jeju Agricultural Research & Extension Services)
• Seong Keun Kang(Research Team for Sustainable Agriculture, Jeju Agricultural Research & Extension Services)