• Korean Journal of Environment and Ecology
• /
• v.33 no.2
• /
• pp.178-186
• /
• 2019

This study used the probit analysis to evaluate the toxicity of three chemicals - benomyl (Germicide), carbofuran (insecticide), and thiobencarb (herbicide) - with the FETAX (Frog Embryo Teratogenesis Assay-Xenopus) protocol using the incubated embryos of tree frog, Hyla japonica. The results showed that the larval body length decreased while the mortality and malformation rates increased as the concentrations of benomyl, carbofuran, and thiobencarb increased. The teratogenic concentration ($EC_{50}$) of benomyl, carbofuran, and thiobencarb were 1.00, 0.58, 4.75 mg/L, respectively, indicating that the malformation of larvae was the most sensitive to carbofuran. The embryo lethal concentration ($LC_{50}$) was 7.04, 28.71, and 16.12mg/L, respectively, indicating that benomyl showed the lowest embryo lethal concentration. The teratogenic index (TI) was 7.04 in Benomyl, 49.50 in Carbofuran, and 3.39 in Thiobencarb, indicating that the TI values were above 1.5, which is the criterion of teratogenicity, for all three chemicals. All three pesticides examined by this study were considered to be the most teratogenic substances, and the carbofuran was the most potent teratogen.

• Korean journal of applied entomology
• /
• v.63 no.1
• /
• pp.13-23
• /
• 2024

Vespa velutina nigrithorax du Buysson, 1905 is the invaded species in Korea since 2003. Since its importance as the honey bee pest, beekeepers use insecticides to kill the adult and immature hornets. However, its legality and effectiveness has not been confirmed. This study investigated the susceptibility of insecticides commonly used to control hornets by beekeepers in Korea. Eight insecticides were tested on adult worker and larvae by topical or oral treatment. Adults showed more than 70% mortalities from Clothianidin, Dinotefuran, and Carbosulfan treatment within 30 minutes. Bifenthrin and Cartap hydrochloride showed relatively low toxicity. The median lethal dose (LD₅₀) for Clothianidin, Dinotefuran, and Carbosulfan was 0.29, 0.65, and 2.21 ㎍/bee, respectively. In larval feeding test where 5^th instar larvae were fed 3 times every 24 hours, the mortality began after second treatments. After 3rd treatments (72 h), all insecticides showed mortality more than 70%. The LD₅₀ values of Clothianidin, Dinotefuran, and Carbosulfan to V. velutina were approximately 10 to 100 times higher than those to honey bee, Apis mellifera. This study provides the basic information of those chemical toxicities to Vespa hornet and honey bees.

• Journal of Sericultural and Entomological Science
• /
• v.26 no.1
• /
• pp.25-29
• /
• 1984

Since 1966, practical use of active heavy analogs of the hormones has been also worked out as an insecticide and brought the features of it to the light as cocoon producer. On the other hand, it is expected to afford the increase of silk productivity resulted from control of the fifth larval period by delaying normal development. With these regards, some of analogs have been tried to apply practically to the silkworm for an increase of cocoon productivity. One of the synthesized juvenile hormone available is "Manina". And it is presently used for the increase of silk productivity in Korea. For the practical use, it is very essential the varietal differences in the increase of silk productivity by topical application was tested and the obtained results are summarized as follows. 1. It was evident that the fifty larval period was extended by topical application after 48 hrs. of the last ecdysis, ranging from 8 hrs. to one day, as compared to the control. 2. In pupal rates, there is no significance between control and treatments. It proved that there was no toxicity to silkworm by topical application in general, except jam 120. With regards to an increase of cocoon yield in Japanese, it was resulted from 17∼24% of cocoon yield from 10,000 larvae, as compared to that of control. In case of Chinese, the incrasing rates were varied from 15∼26% of cocoon yield, 17.8kg of it with 26% increase for Jam 122 and 16.7kg of it with 25% increase for Jam 118. In case of all hybrids, an increase of the cocoon yield took places from 20% to 31% and the weight of cocoon layer for the Japanese increased by 6 to 14%, those for the Chinese by 4 to 7% and those for the hybrids ranged from 21 to 29% increase. 3. It was recognized that the hybrid vigor rate took places with the hybrids between high responsing parents to juvenile hormones.

• Korean journal of applied entomology
• /
• v.47 no.4
• /
• pp.435-445
• /
• 2008

Due to internal feeding behavior, the oriental tobacco budworm, Helicoverpa assulta ($Guen\acute{e}e$), infesting hot pepper has been regarded to be effectively controlled by targeting egg and neonate larval stages just before entering the fruits. This study aimed to develop an efficient biological control method focusing on these susceptible stages of H. assulta. An egg parasitoid wasp, Trichogramma evanescens Westwood, was confirmed to parasitize the eggs of H. assulta. A mixture of Gram-positive soil bacterium, Bacillus thuringiensis subsp. kurstaki, and Gram-negative entomopathogenic bacterium, Xenorhabdus nematophila ANU101, could effectively kill neonate larvae of H. assulta. A sex pheromone trap monitored the occurrence of field H. assulta adults. The microbial insecticide mixture was proved to give no detrimental effects on immature development and adult survival of the wasp by both feeding and contact toxicity tests. A combined treatment of egg parasitoid and microbial pesticide was applied to hot pepper fields infested by H. assulta. The mixture treatment of both biological control agents significantly decreased the fruit damage, which was comparable to the chemical insecticide treatment, though either single biological control agent did not show any significant control efficacy. This study also provides morphological and genetic characters of T. evanescens.

• The Korean Journal of Pesticide Science
• /
• v.11 no.4
• /
• pp.299-304
• /
• 2007

Surveying, laboratory and field trial were performed to elucidate the causes of non-spinning syndrome of silkworm, Bombyx mori, abnormal symptoms of silkworm instars observed in certain sericultural fanning region. Mortality and growth of silkworm was still influenced by feeding the mulberry leaves sprayed with 10,000 fold diluted solution of standard spray of diflubenzuron WP (25%). Mortality and growth of silkworm fed with diflubenzuron-sprayed mulberry leaves with recommended spray solution were entirely affected even six weeks after spraying irrespective to the instars. Larval period of 5th instar and cocooning duration of silkworm was not affected in case 50m of buffer zone has maintained in near-by orchard field sprayed with diflubenzuron WP (25%). However, survival rate of pupae was not influenced in case 100 m of buffer zone has kept. Insect growth regulating insecticides were required to keep a certain distance of buffer zone when sprayed with water-diluted solution, 100 m from the application site at least in order to prevent contamination of the spraying drift by the chemicals.

• The Korean Journal of Pesticide Science
• /
• v.6 no.4
• /
• pp.257-263
• /
• 2002

This study was carried out not only to investigate the toxicities of 12 registered insecticides on different developmental stages, but also to determine the sublethal effects on longevity and reproduction of newly emerged adult female and development of the next generation in the rice skipper, Parnara guttata. Fenitrothion, fenthion, cartap hydrochloride, ethofenprox highly suppressed egg-hatch. All insecticides treated showed high larvicidal activity on the 1st to 2nd instar larva. The insecticides showed higher larvicidal activities on the 5th instar larva were fenitrothion, fenthion, ethofenprox, fipronil, methoxyfenozide, tebufenozide and Bt. var. kurstaki. The sublethal doses of fenthion, tebufenozide, cartap hydrochloride, methoxyfenozide, ethofenprox, imidacloprid and fipronil shortened the longevities of newly emerged adult female from the treated larva ($3{\sim}4$ instar). BPMC, imidacloprid, ethofenprox, fipronil and methoxyfenozide delayed the preoviposition periods of adult females and decreased the number of eggs laid when they were treated at the larval stages of the previous generation. Ethofenprox caused severe sublethal effects on P. guttata offspring, completely blocking the production. All insecticides except fenitrothion affected the egg viability, and all eggs from the adult females emerged from the survivors treated larvae with imidacloprid or fipronil fail to hatch. IGRs, methoxyfenozide and tebufenozide showed an adverse effect on the development of next generation larva.

• The Korean Journal of Pesticide Science
• /
• v.15 no.2
• /
• pp.194-200
• /
• 2011

Diamondback moth (DBM, Plutella xylostella L.) is known as the most destructive pest of cruciferous crops worldwide. As most insecticides targeted to mainly larval stage, new insecticides which have hatching-inhibitory or ovicidal activity could be more efficient to control DBM. Therefore, we developed an easy and efficient method for screening ovicidal activity of DBM eggs using aluminum foil. The aluminum foil ($4{\times}12$ cm) coated with filtered juice of chinese cabbage leave (hereinafter called oviposition foil) exposed to 300 newly-emerged adults for 24 hours inside the rearing container. The oviposition foils were replaced every 4 days consecutively after mating, but it was better to discarded over then. Oviposition foil were divided into 6 to 12 pieces depending on egg mass volume. After dipping into test solutions for 10 seconds using faucet, oviposition foil pieces were placed into common petri dish, and then investigated hatchability. The effect of methanol solvent (50%) for 10 seconds dipping on the toxicity against DBM eggs was negligible. In addition, whether covering the petri dish or not should be dependent on nature of active compounds tested. With applying the new bioassay method, methanol extracts from 50 plants were tested the ovicidal activity to DBM eggs. Among them, four plant extracts; Angelica tenuissima root, Lycium chinense root, Cnidium officinale root and Polygala tenuifolia root, showed high ovicidal activity of over 90% control efficacy, against DBM eggs.

• Korean Journal of Environmental Biology
• /
• v.39 no.3
• /
• pp.311-318
• /
• 2021

In this experiment, we investigated the toxicity of tebuconazole (fungicide) using domestic frog embryos, along the FETAX (Frog Embryo Teratogenesis Assay-Xenopus) protocol. Bufo gargarizans, Hyla japonica, and Pelophylax nigromaculatus embryos were incubated, and investigation of the tebuconazole effect was performed by the probit analysis. As a result, depending on the concentrations of tebuconazole, the mortality and malformation rates were increased and larval body length was decreased. The teratogenic concentrations (EC₅₀) of tebuconazole were 34.4mg L^-1, 10.6mg L^-1, and 14.9mg L^-1, respectively, and the embryo lethal concentrations(LC₅₀) of tebuconazole were 74.7 mg L^-1, 38.5 mg L^-1, and 39.1 mg L^-1, respectively. The teratogenic index (TI) valuesof tebuconazole were 2.19, 3.58, and 2.65; thus, it showed teratogenicity in embryonic development of these three frogs. These results revealed that in this experiment, tebuconazole suppressed the development of embryos at a relatively low concentration. In addition, mortality, malformation ratios, malformation patterns, and growth rates were similar to the results from the other assay systems. Therefore, tebuconazole was thought to have an effect on the embryo development of domestic frogs. In future, it will be necessary to identify species specificity in order to the clarify the causes of differences in mortality, malformation rate, and malformation patterns depending on the species.

• Korean journal of applied entomology
• /
• v.61 no.1
• /
• pp.101-108
• /
• 2022

Because of their specificity to target insects and relatively low toxicity to non-target organisms, insect growth regulators (IGRs) have been regarded as attractive alternatives to chemical insecticides. Commercially available IGRs are classified into juvenile hormone agonists (JHAs), ecdysone agonists (EAs), and chitin synthesis inhibitors (CSIs) according to their mode of action. Recently, JH-mediated interaction of methoprene-tolerant (Met), which is JH receptor, and its binding partners have been replicated in vitro using yeast cells transformed with the Met and FISC/CYC genes of A. aegypti. Using this in vitro yeast two-hybrid β-galactosidase assay, juvenile hormone antagonists (JHANs) have been identified from various sources including chemical libraries, plants, and microorganisms. As juvenile hormone (JH) is an insect specific hormone and regulates development, reproduction, diapause and other physiological processes, JHANs fatally disrupt the endocrine signals, which result in abnormal development and larval death. These results suggested that JHANs could be efficiently applied as IGR insecticides with a broad insecticidal spectrum. This review discuses JH signaling pathway mediated by Met and future prospects of JHANs as environmentally benign IGR insecticides.

• The Sea:JOURNAL OF THE KOREAN SOCIETY OF OCEANOGRAPHY
• /
• v.6 no.4
• /
• pp.265-273
• /
• 2001

The sea urchin has been used as sea food in many countries. This species has also been an important organism of embryological studies for more than a century. In recent years, sea urchin embryos are being used as testing materials for toxicity of pollutants and toxins. Usefulness of sea urchin embryos as experimental models comes from the easiness in obtaining sea urchin samples and a lot of gametes, in rearing embryos in the laboratory, in observing the cellular movement and organ formation during the embryogenesis and in manipulating blastomeres and genetic maferials. The sea urchin in itself is a key organism for the understanding of deuterostome evolution from the protostomes and of indirect development of marine invertebrates which undergo the planktotrophic larval stage. A fertilized sea urchin egg goes through rapid cleavage and becomes a 60 cell embryo 7hr after fertilization. It then develops into a morula, a blastula, a gastrula and finally a pluteus larva approximately 70 hr after fertilization. At the 60 cell stage, the embryo comprises of five territories that express territory-speciflc genes and later form different organs. Micromeres at the vegetal pole ingress into the blastoceol and become the primary mesenchyme cells(PMCs). PMCs express genes involved in skeletogenesis such as SM30, SM37, SM50, PM27, msp130. Among the genes, SM37 and SM50 are considered to be members of a gene family which is characterized by early blastula expression, Glycine-Proline-Glutamine rich repeat structures and spicule matrix forming basic proteins. Genetic studies on the sea urchin embryos help understand the molecular basis of indirect development of marine invertebrates and also of the biomineralization common to the animal kingdom.