Spatial Distribution Pattern and Sampling Plans for Two Sympatric Tomicus Species Infesting Pinus yunnanensis during the Shoot-Feeding Phase

SIMPLE SUMMARY: Tomicus minor (Hartig) and Tomicus yunnanensis Kirkendall and Faccoli are two sympatric species that infest Pinus yunnanensis (Franchet) in southwest China. Sound knowledge of the two pine shoot beetles’ distribution within P. yunnanensis is needed to formulate accurate sampling methods. Three pine forests with different experimental sites in Yuxi, Yunnan province, China were investigated from 2016 to 2018. Field counts were modeled in various spatial models, and it was determined that two species adults showed aggregated spatial distributions. A fixed-precision sampling plan showed that, for a D of 0.25 and 0.10, sample sizes of 41 plants and 259 plants for T. minor and 33 plants and 208 plants for T. yunnanensis were adequate, respectively. This sampling program could be useful for the integrated pest management of two sympatric Tomicus species. ABSTRACT: Tomicus minor (Hartig) and Tomicus yunnanensis Kirkendall and Faccoli are two sympatric species that infest Pinus yunnanensis (Franchet) in southwest China, contributing to growth losses. Accurate sampling plans are needed to make informed control decisions for these species. We investigated three pine forests within experimental sites in Yuxi, Yunnan province, China from 2016 to 2018. The spatial distribution patterns of two pine shoot beetles during the shoot-feeding phase were determined using Taylor’s power law. The optimum sample sizes and stop lines for precision levels of 0.25 and 0.10 were calculated. The model was validated using an additional 15 and 17 independent field datasets ranging in density from 0.06 to 1.90 beetles per tree. T. minor and T. yunnanensis adults showed aggregated spatial distributions. For T. minor, sample sizes of 41 and 259 trees were adequate for a D of 0.25 and 0.10, respectively, while for T. yunnanensis, a mean density of one individual per tree required sample sizes of 33 plants (D = 0.25) and 208 plants (D = 0.10). The software simulations of this sampling plan showed precision levels close to the desired levels. At a fixed-precision level of 0.25, sampling is easily achievable. This sampling program is useful for the integrated pest management (IPM) of two sympatric Tomicus species.