• The Korean Journal of Pesticide Science
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• v.10 no.4
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• pp.335-343
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• 2006

Five strains of Korean entomopathogenic nematodes(EPN), steinernematids and heterorhabditids(Steinernama carpocapsae GSN1, Steinernema sp. GSNUS-10, Steinernama sp. GSNUS-14, Heterorhabditis bacteriophora Hamyang, Heterorhabditis sp. GSNUH-1) were evaluated and tried in petri dish, pot, and vegetable greenhouses for environmentally friendly control of beet armyworm, Spodoptera exigua. $LC_{50}$ values of five EPN strains against beet armyworm was different depending on nematode strain and beet armyworm instar. $LC_{50}$ value of Steinernema carpocapse GSN1(GSN1) was 3.8-5.1 infective juveniles(Ijs) in 2nd to 4th instars of beet armyworm. Pathogenicity of five EPN strains against beet armyworm different in nematode strain, concentration, application times, and vegetable species in pot and greenhouse. Steinernema spp. was more effective than Heterorhabditis spp. against beet armyworm. Two or three times of applications of EPN were found to be effective regardless of nematode strain and concentration in pot and greenhouse. ENP showed different reactions on vegetable species. Efficacy of EPN was higher on Chinese cabbage than that on cabbage and kale. GSN1 was one of the most effective nematodes and 100,000 infective juveniles per $m^2$(720,000 Ijs/$7.2m^2=1{\times}10^9$Ijs/ha) resulted in higher mortality in greenhouse.

• The Korean Journal of Pesticide Science
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• v.6 no.3
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• pp.224-229
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• 2002

In vivo metabolism study was carried out to find out the biochemical or metabolic tolerance mechanism between Diamond backmoth (DBM), Plutella xylostella and Beet armywarm (BAW), Spodoptera exigua to flupyrazofos. They showed some differences between the DBM and BAW. About 20% of flupyrazofos applied to the 3rd instar larvae of DBM was metabolized within 1 h and about 50% of that was metabolized within 4 h. The metabolites of flupyrazofos-oxon in 3rd instar larvae of DBM were increased 10 times more at 4 h than 1 h after application. The amounts of flupyrazol were nearly same between at 1 h and 4 h. The amount of unknown and origin increased 2 and 3 times more at 1 h than 4 h after application, respectively. In the 4th instar BAW larva, about 50% of flupyrazofos was metabolized within 1 h and about 70% of that was metabolized within 4 h. As metabolites, the amounts of flupyrazofos-oxon increased 2 times more at 4 h than 1 h after application. The amounts of flupyrazol increased 4 times more at 4 h than 1 h after application. The amount of unknown and origin increased 2.5 and 2 times more at 4 h than 1 h after application, respectively. From the study, it is supposed that hydrolytic enzyme, esterase, cleave the alkyl bond of flupyrazofos and conjugates with flupyrazofos. This seems to be the main tolerance mechanism of BAW to flupyrazofos.

• Korean journal of applied entomology
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• v.60 no.4
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• pp.363-367
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• 2021

This study was conducted to investigate the EAG (electroantennogram) response of Spodoptera frugiperda male to sex pheromone compounds and whether or not S. frugiperda male adults would undergo double mating. The EAG response of S. frugiperda male adult to Z9-14:Ac increased in a dose-dependent as the dose increased. Among the 7 sex pheromone components investigated, male EAG recording was the highest to Z9-14:Ac. The EAG response of S. frugiperda male adult to the mixed sex pheromone component was greater than that to the single component. Male adults of S. frugiperda were capable of double mating under laboratory condition, and the secondary mating rate increased to 72.2% compared to the 58.3% of primary mating rate. The EAG response of mated S. frugiperda male adult was not different from that of unmated S. frugiperda male. In the net house test with sex pheromone lure, mated male adults were not captured during the test period. Also, strangely, unmated male adults were not captured even in a trap equipped with virgin female adults, although the antennae of mated male adult were responded to the sex pheromone component in the laboratory. Probably, it is thought that the mated male adults may not have been caught in the trap be due to flight ability which has been decreased after mating. The field attractiveness of S. frugiperda male adults to sex pheromones remains to be further elucidated.

• Korean journal of applied entomology
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• v.61 no.2
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• pp.349-356
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• 2022

Fall armyworm, Spodoptera frugiperda, is a invasive migratory pest of native to the tropical and sub-tropical regions that has recently invaded Korea with damage to cornfield. The study was conducted to investigate the development periods of S. frugiperda on artificial diet at six different temperatures. The developmental period from eggs to adult at 18, 21, 24, 27, 30 and 32℃ was 79.8, 54.2, 34.3, 28.4, 24.6 and 24.0 days, respectivery and decreased with increasing temperature. The pupal periods of females were shorter than males. Most of the larvae developed through six instar, but the ratio of 7 or more instar increased at low temperatures. The relationship between the development rate and temperature was fitted with by linear regression analysis. The lower development threshold for egg and larva development was 12.9℃ and 11.3℃, respectively, 12.6℃ for pupae and 11.8℃ for egg-to-adult development. The effective accumulative temperature for the development of the respective life cycle stages were 37.0 DD for eggs, 286.3 DD for larvae, 132.2 DD for pupae and 456.8 DD egg-to-adult development.

• Korean journal of applied entomology
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• v.61 no.1
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• pp.77-83
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• 2022

This study was conducted to determine the optimal composition of sex attractant for monitoring adults of the tobacco cutworm, Spodoptera litura, in Korea. Lures of different compositions from the two sex pheromone components the female, (Z,E)-9,11-tetradecadienyl acetate (Z9E11-14:Ac) and (Z,E)-9,12-tetradecadienyl acetate (Z9E12-14:Ac), were compared for male attraction using synthetic chemicals, rubber septa, and funnel traps in soybean and peanut fields. After sequential tests were conducted using three sets of the two components different ranges from 5:5 to 10:1, from 9:1 to 99:1, and from 9:1 to 39:1, the 19:1 ratio was identified as the most efficient composition. However, S. litura males were barely caught in the trap of the Z9E11-14Ac single component lure. The results show that both the sex attractant compounds are necessary for monitoring adults S. litura males. The higher the pheromone amount in the dispenser in the range from 0.1 to 10 mg, the more males were attracted. Furthermore, the trap height of 1.5 m was optimal for male capture.

• Korean Journal of Agricultural and Forest Meteorology
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• v.25 no.1
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• pp.37-47
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• 2023

The black cutworm, Agrotis ipsilon (Hufnagel), is an important crop pest worldwide that feeds more than 80 plant species including cabbage, potato, maize, wheat and bean, and this moth is a typical pest attacking underground parts of crops. It has been known in farm booklets that the larvae of A. ipsilon overwinter in the soil in Korea, but no definitive data exist yet. This study was conducted to evaluate that the specific appearance time of A. ipsilon observed actually in the field could be explained when we assumed that this pest overwinters in a form of larvae or pupae. Degree day-based phenology models were applied for tracking forward or backward to find the predicted developmental stage which developed at a specific stage found in the field. As a result of the analysis, it was confirmed that an initial population could be established in a group that does not overwinter as larvae or pupae in Korea. In other words, the appearance of adults in early March to April could not be explained by the presence of domestic overwintering populations. Populations that overwinter as larvae or pupae in Korea were able to emerge as adults in June to July at the earliest. Therefore, the group of adults appearing in early spring is highly likely to be a population that migrated from outside Korea. Taken together, it was estimated that the colony of A. ipsilon in Korea would be formed by a mixture of a migrant population through long-distance migration and a overwintering population.

• Korean journal of applied entomology
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• v.40 no.2
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• pp.137-141
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• 2001

This experiment was conducted to investigate the control effect of nuclear polyhedrosis virus and NeemAzal-T/S on Spodoptera litura larvae. In laboratory test, values of$ LT_{50}$ and $LT_{95}$ when treated with S. litura nuclear polyhedrosis virus (SINPV) $1$\times$10^{8}$ PIBs/ml plus NeemAzal-T/S 200 ppm were 1.94 and 8.33 days, respectively. Control effect of the combination of SINPV $1$\times$10^{8}$ plus NeemAzal-T/S 200 ppm was higher than the other concentrations. This mixed treatment could reduce LT$_{95}$ by 3 days. When SINPV alone was sprayed to the S. litura larvae reared on chinese cabbage seedling, the mortalities were 10.7~6.7% at 4 days after treatment. In combinations of SINPV plus NeemAzal-T/S at each level of concentration, the mortalities appeared faster and higher at 4 days after application than single treatment. Especially, the mortalities by combinations of SINPV $1$\times$10^{8}$ /PIBs/ml plus NeemAzal-T/S at 75~200 ppm were 100% at 9 days after treatment. The body weight of untreated larvae was increased 9.4-folds from 235 mg to 2194 mg after 7 days. However, the increasing levels of larval weight were 4.8- and 7.0-folds in the separate treatments of NeemAzal-T/S and SINPV, respectively. Whereas in the combinations of SINPV $10^{4~8}$ PIBs/ml plus NeemAzal-T/S 75~200 ppm, larval weight was increased 3.9 to 2.9-folds. These results showed that the mortality and inhibition of larval weight in the combination of SINPV and NeemAzal-T/S were highly enforced by synergistic effect.

• Korean journal of applied entomology
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• v.48 no.2
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• pp.253-261
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• 2009

For the environment-friendly control of beet armyworm, Spodoptera exigua, in spring onion fields, we have examined an alternative application method. Twenty-five insecticides registered for spring onion were tested for control effect against the beet armyworm in the laboratory, then the best 9 chemical and a single biological insecticides were selected and compared with 2 new isolates of Bacillus thuringiensis in a polyvinyl house. After that, 4 chemical and 3 B. thuringiensis treatments were used in the field for the control of beet armyworm in the spring onion. Two application methods are used: one is triple treatments with the same chemical and the other is alternative application with different chemicals and B. thuringiensis for 7 days intervals. Indoxacarb WP - chlorfluazuron EC - B.t. var. kurstaki CAB141 and indoxacarb WP - methoxyfenozide + spinosad SC - Chlorfluazuron EC - B.t. var. aizawai CAB109, B.t. var. kurstaki CAB141 showed greater than 78% mortality of beet armyworm larvae and greater than 43% damage decrease in spring onions infested by beet armyworm. These results showed that alternative applications had higher control effect than any other applications. It was suggested that alternative applications with microbial biological agents such as B. thuringiensis might minimize the development of insecticide resistance and might be used as the environment-friendly control of the beet armyworm.

• Korean journal of applied entomology
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• v.48 no.2
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• pp.237-243
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• 2009

This study was conducted to develop economic injury level (ElL) and economic threshold (ET) of Cabbage armyworm, Mamestra brassicae L. on cabbage (Brassica oleracea L. var). The changes of cabbage biomass and M. brassicae density were investigated after introduction of larval M. brassicae (2nd instar) at different densities: 0, 1, 2, 4, 8, and 16 larvae per plant at 40 d after planting for an open field experiment, and 0, 2, 5, 8 and 12 larvae per plant at 25 d after planting for a glass house experiment. In the field experiment, the yield loss of cabbage was not significantly different among treated-plots at 30 d after the larval introduction, showing an over-compensatory response of cabbage plants to M. brassicae attack. In the glasshouse experiment, however, the biomass of cabbage at 15 d after the larval introduction significantly decreased with increasing the initial introduced number of M. brassicae, resulting in 38.3, 36.7, 21.7, 23.3 and 16.7g in above treated-plots, respectively. The relationship between cumulative insect days (CID) and yield loss (%) of cabbage was well described by a nonlinear logistic equation. Using the estimated equation, ElL of M. brassicae on cabbage was estimated at 44 CID per plant based on the yield loss 14%, which take into account of an empirical gain threshold 5% and marketable rate 91% of cabbage. Also, ET was calculated at 80% of the EIL: 35 CID per plant. Until a more elaborate EIL-model is developed, the present result may be useful for M. brassicae management at early growth stage of cabbage.

• Korean journal of applied entomology
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• v.47 no.1
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• pp.87-93
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• 2008

Bacillus thuringiensis with selected high toxicities against tobacco cutworm, Spodoptera litura were isolated from domestic soils. When being observed under a phase-contrast microscope, the insecticidal crystal proteins were showed a bipyramidal crystal types. New CAB 109 isolate was identified to B. thuringiensis subsp. aizawai in the H serotype. As a results of insecticidal activities between CAB 109 isolate and 3 existing ready-made products against 3rd larva of S. litura, CAB 109 isolate showed 100% mortality with spore concentration $(1.3{\times}10^7cfu/ml)$. It was a very high insecticidal activity compared with a existing ready-made B. t. products. $LD_{50}$ values of CAB 109 isolate was $9.78{\times}10^5,\;6.87{\times}10^6\;and\;1.83{\times}10^7cfu/ml$ spore concentration against 2nd, 3rd and 4th larva of S. litura, respectively. Unlike Plutella xylostella, S. litura was slowly died after application up to 7 days. The weight of S. litura larva applied with CAB 109 isolate were 6-7 times less than controlled group. Even though it didn't die, it did not grow into next larva. The result observed with scanning electron microscope was that CAB 109 isolate of B. t. aizawai formed a typical bipyramidal crystal protein type. Otherwise, when CAB 109 isolate was examined with SDS-PAGE and with trypsin, there was no difference between CAB 109 strain and ready-made products of B. thuringiensis.