Park S, et al. Korean Circ J. 2024 Apr;54:e42. https://doi.org/10.4070/kcj.2024.0023

Metcalfa pruinosa (Say, 1830) (Hemiptera: Flatidae) has caused substantial agricultural damage since its recent introduction to the Republic of Korea; however, the source of this introduction is still unclear. To examine the genetic divergence and phylogenetic relationships among several populations of M. pruinosa from Korea and foreign countries, 251 COI sequences from 251 samples collected from Korea, France, Italy, Spain, Slovenia, and the United States were newly analyzed, together with seven published COI sequences from Canada. In total, 19 haplotypes were detected from the 258 COI sequences, and three haplotypes, H1, H3, and H9, were detected from samples in Korea. The MJ network and Bayesian inference revealed that the three haplotypes of Korea were closely connected with samples of Italy, Spain, Slovenia, France, and the United States. Our study revealed the possibility of multiple invasions of M. pruinosa from Europe and/or North America into Korea.

An invasive species, Pochazia shantungensis (Hemiptera: Ricaniidae), causes serious economic damage to fruit trees. In Korea, this pest is mainly managed using chemical insecticides. However, the management timing and insecticides for P. shantungensis negatively affect honeybee populations. Thus, this study estimated the decision-making level for P. shantungensis in persimmons to decrease insecticide application and increase management efficiency. We determined which developmental stage (i.e., egg, nymph, and adult) affected the damage-related factors (numbers of new shoots and fruit formations, and harvest amount) of persimmons using both spatial analyses and linear relationships. The distribution of P. shantungensis eggs was spatially correlated with the one of persimmon fruit number. However, we did not find any linear relationships between the densities of P. shantungensis eggs and damage-related factors of persimmons. Instead, we found that the density of P. shantungensis correlated with the death of oviposited branches. From the developed model of branch death possibility based on egg mass density, 5.75 egg masses per newly developed branch were proposed as the decision-making level. The findings would help increase the efficiency of P. shantungensis management in persimmon orchards and develop decision-making levels for other insects.

Even though the optimum sampling methods for invasive pests are very important in newly invaded areas, the standard sampling unit of Ricania shantungensis is still undeveloped in persimmons. Among all developmental stages of R. shantungensis, the egg has close relationship between its density and subsequent tree damage. Thus, this study was conducted to suggest an optimum sampling unit for R. shantungensis eggs in persimmons based on characteristics of its within-tree distribution pattern. The within-tree distribution pattern was characterized with 60 persimmon trees by cutting 12 branches at three vertical levels (low, middle, and high) in four horizontal criteria (east, west, south, and north) per tree. The sampling units were determined based on coefficient of variation (CV) and coefficient of determination (r²) calculated from egg mass numbers per 10 cm from the tip within a branch. In numbers of R. shantungensis egg masses, there was no significant difference (P > 0.05) horizontally, but significant (P < 0.05) difference vertically. More R. shantungensis eggs were found on terminal branches of each trunk. The 60 cm from the tip of branches in the terminal positions of each trunk was selected as the optimum sampling unit for R. shantungensis in persimmons because this unit has the lowest CV value and more than 0.9 of r² value. Even though the optimum sample number per tree should be determined field-specifically, it would be acceptable to sample two or three branches by considering this pests’ recognizable damage level. This small sampling unit could make the sampling of R. shantungensis become more economical, precise, and consistent in persimmon fields.