A previous studies depicting origin and sequence variability of the species using DNA barcoding region with the samples collected from Korea showed relatively low sequence variability. Thus, additional markers that reveal higher variability were necessitated to scrutinize population structure in connection with dispersal and invasive dynamics among international populations. Therefore, we sequenced two complete mitochondrial genomes (mitogenomes) of M. pruinosa from the two haplotypes occurring in Korea (H1 and H3). Comparison of the two mitogenomes each with 16,312 and 16,314 bp evidenced that one region located in the A+T-rich region to provide higher number of haplotypes (4 vs. 3), sequence divergence (1.636% vs. 0.636%), and variable sites (7 vs. 3) than those of DNA barcoding region from the screening test using 13 representative individuals. This variable region, in concatenation with the currently available DNA barcoding region might be useful for population genetic analysis of worldwide populations including those of Korea. †These authors contributed equally to this paper.

The citrus flatid planthopper, Metcalfa pruinosa is one of the invasive insect species in South Korea. M. pruinosa is a broad polyphage damaging over 200 plant species including ginseng, although there is a difference in preference. We selected six insecticides that showed high mortality in ginseng field such as emamectin benzoate EC, sulfoxaflor SG, etofenprox EW, cypermethrin EC, thiacloprid SC and pyrifluquinazon SG. In addition, a method to attract and kill M. pruinosa by treating pesticides on attractive plants (e.g., corn, perilla) with high preference was also tested. The control effect varied from 10 to 80% depending on the distance between forest and farmland. These methods can be used for the control of M. pruinosa in the ginseng farm when the PLS (Positive List System) is fully implemented in 2019.

Eighty kinds of pesticides registered in the peach and leaf perilla were assessed the efficacy against the 4th nymph stage of citrus flatid planthopper. Plant of Sharon, host plant preferred by citrus flatid planthopper, was cut from 5 to 7 cm and dipped 10 seconds into recommended concentrations of pesticides, respectively, and then dried naturally for the 30 minutes. New shoot of Plant of sharon treated pesticides and 10 to 15 final nymphs of citrus flatid planthopper put together in the 50㎖ tube and the number of live nymphs was investigated after 48 hours. Pesticides showing mortality over 90% were seven, namely, bifenthrin EW, Rhamda-cyhalothrin EC, Clothianidin SC, Benfuracarb SG, Chloropyrifos WP, Bifenthrin+methoxypenozide SC, Chloropyrifos+imidacloprid WP. When the forest surrounding the peach and leaf perilla was occurred and damaged by citrus flatid planthopper, the use of these pesticides is judged to be effective in the control of this pest.

The insecticidal activity of cinnamon essential oils, cinnamon bark, cinnamon technical, cinnamon green leaf oils and their constituents and structurally related compounds against citrus flatid planthopper, Metcalfa pruinosa, was examined using a direct contact application. At 500 mg litre-1 very strong mortality (100%) was observed in cinnamon technical, cinnamon bark, cinnamon green leaf, mortality against flatid planthopper M. pruinosa. The cinnamon oils constituents were identified by GC-MS. The active principles were determined to be hydrocinnamic acid (24 h LC50, 30.66 mg/L), geranic acid (24 h LC50, 31.23 mg/L), cinnamaldehyde (24 h LC50, 32.65 mg/L), hydrocinnamaldehyde (24 h LC50, 39.11 mg/L) and trans-cinnamaldehyede (24 h LC50, 39.54 mg/L) were the most toxic against both nymph and adult of citrus flatid planthopper, M. pruinosa. The moderate activity was observed with cinnamyl acetate, dibutyl pthalate, anethole, α -cyano cinnamic acid, cinnamyl alcohol, methyl cinnamaldehyde, eugenol, 2.4-dihydrocyl cinnamic acid, bornyl acetate (24 h LC50, 53.35- 97.17 mg/L) respectively. The other constituents were showed less or no activity against adult of M. pruinosa. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active cinnamon oils active principles act as potential insecticides for the control of M. pruinosa populations as direct spray with contact action.

The insecticidal activity of 120 plant essential oils and control efficacy of six experimental spray formulations (SF) containing the oils (SF-0.25, 0.5, 1, 2.5, 5 and 10% sprays) against both nymph and adult of citrus flatid planthopper, Metcalfa pruinosa, was examined using a direct contact application. Reponses varied according to dose (1000 mg litre-1 and 500 mg litre-1). Based on 24 h exposure in leaf dipping assay at 1000 mg litre-1 strong mortality was observed in more than 19 essential oils among 130 was screened. At 500 mg litre-1 very strong mortality (100%) was observed in cinnamon technical, cinnamon green leaf, cinnamon #500, cassia tree, citronella java and penny royal followed by origanum, thyme white, grape fruit, savory, fennel sweet, aniseed and cinnamon bark (93.3- 80%) showed considerable moratality against nymphs of M. pruinosa. The moderate mortality was found in thyme red, tagette, calamus, lemoneucalptus and geranium (73.3-60%). The other oil has low or very low mortality against M. pruinosa. The oil applied as SF-10% sprays provided 100% mortality against adult M. pruinosa. In particular cinnamon technical showed very strong (>SF-0.5= 100%) effect followed by cinnamon #500 (>SF-2.5=100%), cinnamon green leaf (>SF-2.5=100%) and penny royal (>SF-2.5=100%) respectively. Global efforts to reduce the level of highly toxic synthetic insecticides in the agricultural environment justify further studies on the active essential oils as potential larvicides for the control of M. pruinosa populations as direct spray with contact action.