• Korean journal of applied entomology
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• v.43 no.2
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• pp.175-180
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• 2004

This study was conducted to determine the effect of sublethal concentrations ($LC_{10}$ and $LC_{30}$) of insecticides on pupal duration, emergence, adult longevity and oviposition of tobacco cutworm, Spodoptera litura Fabricius, when 3rd instar larva of tobacco cutworm was treated with insecticides of chlorpyrifos, ethofenprox, chlorfenapyr-bifenthrin and hexaflumuron-chlorpyrifos . Pupal duration of female and male were 6.9 days and 8.0 days at untreatment, and were 7.2 to 7.6 days and 8.3 to 8.6 days at insecticide treatment, respectively. Thus pupal duration at the insecticide treatment was slightly longer than that at the untreatment, and that of the males was slightly longer than that of the females even though significant difference between sublethal concentrations and among insecticides was not observed. Percent mergence was 88％ at untreatment and ranged from 79％ to 95％, in particular which showed above 91％ treated with chlorfenapyr-bifenthrin and ethofenprox, at insecticide treatment. Adult longevity was 7.7 days and 7.9 days for female and male at untreatment respectively, and 7.1 to 8.4 days for female and 7.7 days to 9.0 days for male at treatment. There was a significant difference between insecticides and sublethal concentrations of insecticides except showed the longest adult longevity at hexaflumuron-chlolfyrifos treatment. Total number of eggs laid were less at treatment (778-948) than that (1,010) at untreatment regardless of sublethal concentrations of insecticides. Accordingly the pupal duration and oviposition of tobacco cutworm were affected at the insecticide treatment of sublethal concentration.

• Journal of fish pathology
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• v.26 no.1
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• pp.1-9
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• 2013

The acute toxicity and sublethal effects of nitrite on the dark-banded rockfish, Sebastes inermis (mean body weight: $83.3{\pm}7.2$ g), were studied under static conditions for a period of 96 h. The acute toxicity of nitrite was at the 50% lethal concentration ($LC_{50}$) of 700 mg/L. The sublethal effects on selected hematological parameters of the dark-banded rockfish, such as its osmolality, hematocrit, cortisol, alanine aminotransferase (ALT), and aspartate aminotransferase (AST), were measured after 0, 6, 12, 24, 48, 72, and 96 h of exposure to 0, 50, 100, 200, 400, or 700 mg/L nitrite. Sublethal nitrite caused a progressive reduction in the hematocrit of the fish, depending on the nitrite concentration and the exposure period. Exposure to 100-700 mg/L nitrite for 96 h caused a reduction in the hematocrit and an increase in cortisol, ALT, and AST compared with the control levels. Abnormal ultrastructural changes in the gills and liver tissues were observed in fish exposed to 700 mg/L nitrite for up to 96 h compared with the control tissues. Ultrastructural changes included atrophic gill mitochondria and hepatocytes that developed smooth endoplasmic reticulum and atrophic mitochondria. Although no rockfish mortality occurred at 500 mg/L nitrite, all the hematological parameters examined responded adversely to a nitrite dose of 200 mg/L for 96 h. These results show that although the acute toxic concentration of nitrite for the dark-banded rockfish is > 700 mg/L, sublethal concentrations of nitrite also negatively affect its hematological parameters.

• Ocean and Polar Research
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• v.28 no.1
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• pp.45-56
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• 2006

This study investigated primarily the toxic effects of bis(tributyltin)oxide (TBT) and DDT (Dichlorodiphenyltrichloroethane) on the mortality of adult Acartia omorii and barnacle nauplii as well as the hatching rate of A. omorii. Subsequently, compound effects of TBT and DDT on the mortality of immature copepods were tested in order to assess whether or not synergistic influence existed in the mixture of sublethal concentration of two pollutants. Mortality of adult A. omorii increased as exposure concentration of DDT increased in the range of from 0.0001 to 1ppm. Egg hatching rate of the copepod showed no distinctive difference in the range between 0.1 and 10ppm, while barnacle nauplii showed abnormal motility of their appendages in the range of 0.0001 to 1 ppm. Mortality of adult A. omorii increased as TBT concentration increased within the range of 1 and 10 ppb, whereas egg hatching rate of the copepod showed no linear response to the same exposure range. Moreover, copepod nauplii were almost motionless even though copepod eggs hatched under the exposure condition of TBT $(0{\sim}10 ppb)$ and DDT $(0{\sim}10 ppm)$, respectively, suggesting that the nauplii are hard to develop into adult stage. On the basis of the sublethal concentration less than the 24-h $LC_{50}$, 0.001 ppm (DDT) and 2 ppb (TBT) were selected to confirm the compound effects of two pollutants on the mortality of immature copepods. Mortality of immature copepods under the condition of mixture of the two pollutants was higher than that in the single exposure condition. This result seems to indicate that synergistic effects of sublethal toxicants can make a more hazardous effect on the survival of immature copepods even though the concentration of single toxicant is not lethal to copepods in the marine environment.

• Korean Journal of Food Science and Technology
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• v.38 no.5
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• pp.720-723
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• 2006

The viability of Shigella sonnei, a significant cause of gastroenteritis in Korea, on TSA plates was determined after sublethal heating treatments and NaCl treatments. In addition, recovery levels of sublethally injured cells on TSA plates containing different concentrations of NaCl (TSAS) were investigated. The viability decreased significantly with increasing degree of sublethal heating treatments, but increases in NaCI treatment concentration from 0 to 6% had little effect on the viability. After being sublethally treated at $55^{\circ}C$ for 30 min, bacterial populations were reduced by 7.58, 7.83 and 7.93 log CFU/mL on 2, 4, and 6% TSAS, respectively. After being sublethally treated at $60^{\circ}C$ for 30 min, bacterial populations were reduced by 6.71, 6.73, and 6.73 log CFU/mL on 2, 4 and 6% TSAS, respectively. Decimal reduction times (D-values) decreased with increasing NaCl treatment concentrations after sublethal heating at 55 or $60^{\circ}C$. These data imply that the S. sonnei cells sublethally injured by insufficient heating processes had a lower recovery rate with increasing NaCl concentrations in the recovery media.

• Journal of Microbiology and Biotechnology
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• v.14 no.6
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• pp.1211-1216
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• 2004

A MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) induced chromium resistant strain ($Cr^{r}18$) of unicellular cyanobacterium Anacystis nidulans has been isolated and characterized. The resistant strain could grow (although restricted to $50\%$ of control) in chromium concentration (180${\mu}M$) lethal to the wild-type. Sublethal ($160{\mu}M$) concentration of $Cr^{6+}$ significantly reduced (13-$37.5$) all the photosynthetic pigments of A. nidulans with maximum reduction in phycoerythrin followed by ChI $\alpha$. Pigments of A. nidulans were drastically decreased in lethal concentration of Cr^{6+} with maximum reduction in phycoerythrin ($75\%$) and allophycocyanin ($67.5\%$). Resistant strain $Cr^{r}18$ resisted toxic effects of sublethal and lethal concentrations of $Cr^{6+}$ on photosynthetic pigments as revealed by less decrease in pigments as compared to A. nidulans. Effect of $Cr^{6+}$ stress was also studied on nitrogen assimilation and phosphate uptake. Sublethal concentration of $Cr^{6+}$ drastically reduced ($71.5\%$) nitrate uptake by A. nidulans while a decrease of $29\%$ was observed in strain $Cr^{r}18$. Short (2 day) exposure of A. nidulans and its resistant strain $Cr^{r}18\;to\;Cr^{6+}$ did not affect nitrate reductase and glutamine synthetase (transferase), whereas longer (10 day) exposure to $Cr^{6+}$ lowered activities of both enzymes in A. nidulans but not significantly in the strain $Cr^{r}18$. Ammonium uptake by both strains was not affected by $Cr^{6+}$. Thus, $Cr^{6+}$ affected photosynthetic pigments, nitrogen assimilation, and phosphate uptake of A. nidulans, while strain $Cr^{r}18$ was able to resist toxic effects of the metal. Advantages of using strain $Cr^{r}18$ for bioremediation purposes have been evaluated by studying $Cr^{6+}$ removal from the solution. Resistant strain $Cr^{r}18$ was able to remove $33\%$ more $Cr^{6+}$ than A. nidulans and thus it can prove to be a good candidate for bioremediation of $Cr^{6+}$ from polluted waters.

• The Plant Pathology Journal
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• v.39 no.3
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• pp.290-302
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• 2023

Abamectin offers great protection against Bursaphelenchus xylophilus, a well-known devastating pathogen of pine tree stands. Trunk injection of nematicides is currently the most preferred method of control. This study aimed to evaluate the potency of the commonly used formulations of abamectin against B. xylophilus. Twenty-one formulations of abamectin were evaluated by comparing their sublethal toxicities and reproduction inhibition potentials against B. xylophilus. Nematodes were treated with diluted formulation concentrations in multi-well culture plates. And, populations preexposed to pre-determined concentrations of the formulations were inoculated onto Botrytis cinerea culture, and in pine twig cuttings. Potency was contrastingly different among formulations, with LC₉₅ of 0.00285 and 0.39462 mg/ml for the most, and the least potent formulation, respectively. Paralysis generally occurred at an application dose of 0.06 ㎍/ml or higher, and formulations with high sublethal toxicities caused significant paralysis levels at the tested doses, albeit the variations. Nematode reproduction was evident at lower doses of 0.00053-0.0006 ㎍/ml both on Botrytis cinerea and pine twigs, with significant variations among formulations. Thus, the study highlighted the inconsistencies in the potency of similar product formulations with the same active ingredient concentration against the target organism, and the need to analyze the potential antagonistic effects of the additives used in formulations.

• The Plant Pathology Journal
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• v.39 no.1
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• pp.75-87
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• 2023

The pine wood nematode (PWN), Bursaphelenchus xylophilus is a well-known devastating pathogen of economic importance in the Republic of Korea and other countries. In the Republic of Korea, trunk injection of nematicides is the preferred method of control. In this study, the efficacy of 16 locally produced formulations of emamectin benzoate against the PWN are compared through determining their sublethal toxicities and reproduction inhibition potentials. Nematodes were treated with varying concentrations of the tested chemicals in multi-well culture plates, and rates of paralysis and mortality were determined after 24 h. Reproduction inhibition potential was tested by inoculating pre-treated nematodes onto Botrytis cinerea, and in pine twig cuttings. Despite the uniformity in the concentration of the active ingredient, efficacy was contrastingly different among formulations. The formulations evidently conformed to three distinct groups based on similarities in sublethal activity (group 1: LC₉₅ of 0.00768-0.01443 mg/ ml; group 2: LC₉₅ of 0.03202-0.07236 mg/ml, and group 3: LC₉₅ of as high as 0.30643-0.40811 mg/ml). Nematode paralysis generally occurred at the application dose of 0.0134-0.1075 ㎍/ml, and there were significant differences in nematode paralysis rates among the products. Nematode reproduction was only evident at lower doses both on B. cinerea and pine twigs, albeit the variations among formulations. Group 1 formulations significantly reduced nematode reproduction even at a lower dose of 0.001075 ㎍/ml. The variations in efficacy might be attributed to differences in inert ingredients. Therefore, there is need to analyze the potential antagonistic effects of the large number of additives used in formulations.

• The Korean Journal of Soil Zoology
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• v.3 no.1
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• pp.9-16
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• 1998

Effects of temperature, pH, and salt concentration on the preservation of the infective juvenile entolopathogenic nematodes, Steinernema carpocapsae, were analyzed. The effects of acclimation to sublethal low temperature and glycerol concentrations on rapid cold hardening of the nematodes were also evaluated to set up the conditions for their cryopreservation. All tested environmental factors could change the storage effectiveness of the nematodes. These analyses indicated that the optinal storage condition for the nematodes consisted of $15^{\circ}C$, pH 8.5, and 0.5-1.0% salt concentration. The nematodes showed a rapid could hardening in response to $5^{\circ}C$ for 2h. Glycerol induced the nematodes to increase the cold hardiness. Its high concentration over 10%, however, gave a harmful effect on the nematode survival.

• Proceedings of the Zoological Society Korea Conference
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• 2000.10a
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• pp.159.2-160
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• 2000

No Abstract, See Full Text

• Environmental Analysis Health and Toxicology
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• v.17 no.3
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• pp.219-224
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• 2002

This study was carried out to examine the effects of bis (tribytyltin)oxide (TBT), endocrine disrupting compounds (EDCs). on the changes of survival, growth and oxygen consumption rate in the oliver flounder, Paralichthys olivaceus. Oliver Flounders were exposed to sublethal concentration of TBT (0, 1.67, 3.20, 6.30 and 12.50 $\mu\textrm{g}$/L) during 6 weeks. Survival rate was decreased in a concentration and exposure period-dependent way and suddenly the reduction of more than 20% occurred at TBT concentration greater than 3.20 $\mu\textrm{g}$/L. after exposure 6 weeks. Growth rate and feed efficiency significantly decreased at concentration greater than 3.20 $\mu\textrm{g}$/L. Oxygen consumption rate was also decreased in a concentration-dependent way and significantly decreased to 17,48 and 67％ than that of the control at the TBT concentration of 3.20, 6.32 and 12.50 $\mu\textrm{g}$/L, respectively. This study revealed that high TBT concentration ($\geq$3.20 $\mu\textrm{g}$/L) reduced growth and oxygen consumption rates of the juvenile oliver flounder suggesting potential influence on the natural mortality of Paralichthys olivaceus in the coastal areas.