Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae) is a worldwide polyphagous pest. The management of this pest have mainly relied on chemical agents. However, the overuse is harmful to the environment and results in insects resistance. Therefore, alternative eco-friendly control methods that have different mode of action, such as biological control, are necessary to overcome the current issue. In this study, we isolated entomopathogenic fungi from Korean soil, and characterized them via morphological and molecular techniques and pathogenicity assay against Tenebrio molitor larvae. The isolated fungi were screened for virulence against T. palmi under laboratory conditions and the results were used to establish a thrips-pathogenic fungal library. The highly virulent isolates were selected and further characterized for optimum culture conditions and application as biopesticide in the field.

A residual contact vial plus water (RCVpW) bioassay method was established to monitor insectiside resistance in field populations of the melon thrips, Thrips palmi. Resistance level against six major insecticides were evalutated in five regions to test applicability of RCVpW as an on-site resistance monitoring tool. Reduced mortality in response to six test insecticides were exhibited compared to the RDA susceptable strain showing 100 % mortality, indicating different degree of resistance. An apparently reduced mortality to emamectin benzoate and chlofenapyr was observed in some field populations, suggesting uneven distribution of resistance to these insecticides in field populations. In addition, spinosad resistance was high and widely distributed in the test regions. Synergistic bioassay revealed that cytochrome P450-mediated metabolic factor is involved in spinosad resistance in the Korean population.

오이총채벌레(Thrips palmi Karny)는 동남아시아지역이 원산으로 국내 침입 외래해충이다. 주로 노지와 하우스에서 재배되는 박과(Cucurbitaceae)와 가지과(Solanaceae) 작물에 직접 섭식과 바이러스 매개에 의한 피해가 크다. 본 연구에서는 차세대염기서열분석기술(NGS)을 통해 오이총채벌레의 미토콘드리아 전장 게놈을 해독하였으며 염기서열 신규 조립(de novo assembly) 결과 전체 길이가 16,414bp인 원형의 유전체로 추정되었다. 미토콘드리아 게놈 전체에서 뉴클레오티드는 A와 T가 78.5%를 차지는 특징을 보였다. 동물의 미토콘드리아 게놈에서 일반적으로 발견되는 37개 유전자 영역에 대해 BLAST 검색을 한 결과 trnV는 탐색되지 않았다. 본 발표에서는 신규 조립된 오이총채벌레 미토콘드리아 게놈 유전체에 포함된 유전자의 종류와 배열 등에 대한 기초 통계자료를 정리하였다.

Residual contact vial (RCV) method was used to monitor insecticide resistance in field populations of the melon thrips, Thrips palmi. Median lethal doses (LD50) at 8 h post-treatment of six insecticides (chlorfenapyr, cyantraniliprole, cypermethrin, dinotefuran, emamectin benzoate and spinosad), which are commonly used for T. palmi control, were determined at 8 h post-treatment using a susceptible RDA strain. The diagnostic doses for on-site resistance monitoring of the six insecticides, which were determined as two-fold higher doses of LD90 for the RDA strain, were in the range of 0.299 to 164,25 μg-1cm2. To test the applicability of RCV for T. palmi, insecticide resistance levels in three field populations (Gyeonggi; GG_AS, Chungbuk; CB_CJ, Jeonbuk; JB_KJ) were evaluated. Field populations showed reduced mortality (0-50% mortality) to spinosad, cypermethrin, cyantraniliprole and emamectin benzoate, that they have different degree of resistances to these insecticides. In particular, all test field populations exhibited 0% mortality to spinosad, suggesting wide spread of spinosad resistance in the field. Moreover, no detectable mortality to emamectin benzoate was observed in JB_KJ strain, suggesting uneven distribution of emamectin benzoate resistant population of T. palmi. To provide more precise information on resistance profiles and distribution in T. palmi populations, it would be necessary to conduct a large scale resistance mapping for broad geographical regions.

Melon thrips, Thrips palmi Karny (Thysanoptera: Thripidae) is a serious insect pest of various crops in the world. The management of this pest mainly have relied on chemical agents. However, the overuse of chemical agents for long times causes insect resistance, and negative effects on environment. Therefore, alternative control methods, such as biological control, that are less harmful to the environment and have different mode of action are needed to control this pest. In this study, we isolated entomopathogenic fungi from Korean soil, and characterized them via morphological and molecular identifications and pathogenicity check against Tenebrio molitor larvae. The isolated fungi were subjected to virulence assay against T. Palmi with a conidial suspension of 1×107 conidia/ml in laboratory conditions. This entomopathogenic fungi library would be a good resource to select effective strains for the control of T. palmi in fields.

This study was aimed at assessing the fumigant toxicity to adult Thrips palmi and Orius strigicollis of basil (Ocimum basilicum) essential oil compounds and structurally related compounds using vapour-phase toxicity bioassays. Results were compared with those for dichlorvos. Against adult T. palmi, linalool (LD50, 0.0055 mg cm–3) was the most toxic fumigant and was 15.2–fold more effective than dichlorvos (0.0837 mg cm–3). Strong fumigant toxicity was also observed in pulegone (0.0095 mg cm–3), (±)-camphor (0.0097 mg cm–3) and 1,8-cineole (0.0167 mg cm–3). Moderate toxicity was produced by camphene, 3-carene, (–)-menthone, (+)-α-pinene, (+)-β-pinene, α-terpineol and (–)-α-thujone (0.0215–0.0388 mg cm–3). Against adult O. strigicollis, dichlorvos (LD50, 9.0 ×10–10 mg cm–3) was the most toxic fumigant, whereas the LD50 values of these compounds ranged from 0.0127 to >0.23 mg cm–3. Based upon selective toxicity ratio (STR, O. strigicollis LD50/T. palmi LD50), the compounds described (STR, 0.7–>10.7) are more selective than dichlorvos (STR, 10.8×10–9 mg cm–3). Basil oil compounds described merit further study as potential insecticides for control of T. palmi in greenhouses because of their generally lower toxicity to O. strigicollis and their greater activity as a fumigant than dichlorvos.

Thc climate change has the potential to significantly modify the actual distribution of insect pest with unknown consequences on agricultural systems and management strategies. In this study, Thrips palmi Karny was selected to predict distribution under climate change. T. palmi was introduced and first recorded in 1993 in Korea, and has become a serious pest of vegetable and ornamental crops. The MaxEnt was applied to T. palmi to predict its potential geographic distribution in Korea and Japan under the RCP 8.5 climate changing scenario. The MaxEnt software package is one of the most popular tools for species distribution and environmental niche modeling. The habitat prediction model of T. palmi in Korea was validated by the distribution of T. palmi in Japan. Based on the MaxEnt modeling, T. palmi would expand their potential distribution to whole Korean peninsula except the alpine region in Gangwon-do and Yanggang-do and Hamgyeongbuk-do in 2070s. Therefore, the monitoring system and management strategy for T. palmi should be reconsidered and re-evaluated.

Cold tolerance of the palm thrips, Thrips palmi Karny, was investigated to predict its survival in field during winter. Supercooling temperatures of T. palmi ranged from -26.4 to -18.4°C. However, exposure to subzero temperatures (from -5°C to -15°C) gave significant mortality to all developmental stages of T. palmi. Thus, T. palmi was determined to be a freeze-susceptible and suffered with cold injury. A brief pre-exposure to a low temperature (4°C) for 7 h significantly increase the cold tolerance of all stages of T. palmi with respect to survival at -10°C and supercooling capacity. A pre-exposure of T. palmi at 4°C significantly increased the survival rate on all developmental stages at -10°C. The rapid cold hardiness (RCH) was dependent on the duration of the pre-exposure period at 4°C in adult stage. Cryoprotectant analysis using an HPLC showed that the pre-exposure treatment increased the adult to synthesize glycerol, trehalose, mannitol, and mannose, at which trehalose represented the highest content. This study suggests that all stages of T. palmi are able to become cold-hardy by RCH, in which several polyols may play crucial roles as cryoprotectant.

Thrips palmi Karny was introduced and first recorded in 1993 in Korea. This species has become a serious pest of vegetable and ornamental crops. CLIMEX simulation was applied to T. palmi to predict the potential geographic distribution in Korea under the Representative Concentration Pathway (RCP) 8.5 climate change scenario. In the CLIMEX simulation, ecoclimatic index (EI) was calculated, and compared in each simulated year and each simulated location. The map comparisons showed a good agreement between simulated and present distributions of T. palmi, indicating that the CLIMEX model was well explained and appropriate for prediction of future distributions of this species in Korea. In near future, until a year of 2020, all the western and eastern parts of Korea showed favorable to marginal suitability for T. palmi populations in fields. After the year of 2040, the potential distributions are shifted from no persistent to favorable for establishment and persistence from coastal to interior of the Korean peninsula except a north-eastern interior region which is the northernmost part of high mountains (Baekdu-Daegan) area in South Korea. Based on simulation results, T. palmi would overcome its weather restriction in near future under a severe climate change scenario, thus, pest management measures and strategies should be re-constructed in Korea, with further studies including interspecific competition and understanding ecosystem change due to climate change.