Dioryctria abietella and D. sylvestrella are among the most damaging shoot/cone pest insects in the Korean pine plantations in Heilongjiang Province, China. The Iwao’s patchiness regression models and seven aggregation indexes were used to analyze the data. The distributions of D. abietella and D. sylvestrella larvae in all four cardinal directions of the pine trees were not significant different. The cone damaged rates and larval densities of D. abietella in the high cone-bearing plots were significantly higher than those in the low cone-bearing plots;however, no significant differences of these two variables for D. sylvestrella were found between the high and low cone-bearing pine plots. The seven aggregation indexes showed that the larvae of both species had aggregated spatial distribution, and the basic distribution component is the individual insect. The individuals of D. abietella larvae were exclusive of each other, whereas the individuals of D. sylvestrella larvae attracted to each other on the Korean pine trees.λ>2 indicates that the aggregation distribution is likely caused by both their aggregation behaviors and environmental factors. The optimal sampling sizes and sequential sampling plans for larvae of these two moth species in different levels of cone-bearing pine stands were calculated through the Iwao’s m *-m regression coefficients:α and β. Therefore, the larval spatial distribution patterns of D. abietella and D. sylvestrella were both aggregated, but their intra-specific individual relationships were different between these two Dioryctria species. Based on the sampling techniques/plans, one can estimate the moth population trends/dynamics and then take optimal measures to control these economically important pest insects.
Journal of Northeast Forestry University