• Korean journal of applied entomology
• /
• v.52 no.1
• /
• pp.35-43
• /
• 2013

All tested Korean populations of the diamondback moth, Plutella xylostella, are known to be resistant especially against pyrethroid insecticides by mutation in its molecular target, para-sodium channel. Moreover, P. xylostella is able to develop resistance against most commercial insecticides. This study was performed to develop an efficient control technique against P. xylostella by a combined treatment of an endoparasitoid wasp, Cotesia plutellae, and a microbial insecticide, Bacillus thuringiensis. To investigate any parasitism preference of C. plutellae against susceptible and resistant P. xylostella, five different populations of P. xylostella were compared in insecticide susceptibilities and parasitism by C. plutellae. These five P. xylostella populations showed a significant variation against three commercial insecticides including pyrethroid, organophosphate, neonicotinoid, and insect growth regulator. However, there were no significant differences among five P. xylostella populations in their parasitic rates by C. plutellae. Moreover, parasitized larvae of P. xylostella showed significantly higher susceptibility to B. thuringiensis. As an immunosuppressive agent, viral ankyrin genes (vankyrins) encoded in C. plutellae were transiently expressed in nonparasitized larvae. Expression of vankyrins significantly enhanced the efficacy of B. thuringiensis against the third instar larvae of P. xylostella. Thus an immunosuppression induced by C. plutellae enhanced the insecticidal efficacy of B. thuringiensis. These results suggest that a combined treatment of C. plutellae and B. thuringiensis may effectively control the insecticide-resistant populations of P. xylostella.

• Korean journal of applied entomology
• /
• v.33 no.4
• /
• pp.225-229
• /
• 1994

The methanol extracts from 30 species of oriental medicinal plants belonging to 24 families were tested for their lhicidal and antifeeding activit~es against diamondback moth (Plutello xylostella L) and tobacco cutworn (Spodoptera litura F.) by a leaf-dipping method at a concentration of 5, 000 ppm. The methanol extract from Copti chinensis only showed a potent larvicidal activity against P xylostello. Strong antifeeding activity against P. xylostello was observed from the extmds from Platycodon grandiflorurn, Codonopsis pilosula, Asomm sieboldii, Rhus chinensis and Uthospermum erythrorhizon And a potent antifeeding activity against S. liturn was obtained from Akebia quinata and Equlsetum hyemale extracts. A significant antifeeding activity against both species was obtained from R chinensis and C. chinensis extracts.

• The Korean Journal of Pesticide Science
• /
• v.4 no.1
• /
• pp.44-50
• /
• 2000

Tolerance mechanism to flupyrazofos was examined with Plutella xylostella (L.) and Spodoptera exigua by investigating the penetration rate of flupyrazofos into larvae body. On determining effective washing of $^{14}C$-flupyrazofos, the washing volume to recover over 98% of $^{14}C$-flupyrazofos was observed at three times (each time: 1 mL). To select a suitable solvent, the recovery rates of each solvent in 3rd instar larvae of DBM were above 98%, but the washing rates of acetone, hexane and ethyl-acetate were 85.1%, 67.2% and 68.4%, respectively. In the BAW larvae, although the recovery rates of each solvent were above 99%, the washing rates of acetone, hexane and ethyl-acetate were 83.5%, 65.9% and 71.7%, respectively. The $PT_{50}$ values of $^{14}C$-flupyrazofos were 0.731 h (44 min) in the DBM larva and 0.504 h (30 min) in the BAW larva. Radiocarbon in acetone washing (external fraction) decreased more quickly in the BAW larva than in the DBM larva, and amount of radiocarbon in larvae body increased more quickly with time in the DBM larva than in the BAW larva. In contrast, amount of radiocarbon in excreta increased more rapidly with time in the BAW larva than in the DBM larva.

• The Korean Journal of Pesticide Science
• /
• v.13 no.3
• /
• pp.197-202
• /
• 2009

Based on the insecticidal efficacy by insecticide treatment methods, neurophysiological responses were compared with the larvae of diamondback moth (DBM) and beet armyworm (BAW) using pyrethroids working on nervous system. By body spray method, all pyrethroids were showed lower insecticidal activity below 50% on the larvae of DBM and BAW. By leaf dipping method, DBM larvae were showed the insecticidal activity as 100% at 50 ppm deltamethrin, 80.0% at fenvalervate and 63.3% at permethrin. However, BAW larvae were showed lower insecticidal activity as similar as control in all concentration. In order to examine electrophysiological response on nervous system on DBM and BAW larvae when treated three insecticides, we investigated the voltage and reaction degree. The voltage of DBM were responded as high as $10^{-7}M$ in deltamethrin, $10^{-5}M$ in fenvalerate and $10^{-3}M$ in permethrin. However, those of BAW were showed dull responses with small variation of voltage to all three insecticides.

• Korean journal of applied entomology
• /
• v.49 no.2
• /
• pp.129-137
• /
• 2010

Four major agricultural insect pests, Bemisia tabaci, Myzus persicae, Plutella xylostella and Tetranychus urticae, were irradiated with 30, 50, 70, or 100 Gy electron-beam. Longevity, egg hatching, emergence, and fecundity of the test insects were measured. Hatchability of B. tabaci, P. xylostella and T. urticae declined with increasing irradiation doses, and all B. tabaci and T. urticae eggs were dead at 100 Gy. When eggs of B. tabaci, P. xylostella and T. urticae were irradiated, hatch was inhibited. B. tabaci adults grown from 70 Gy irradiated eggs did not lay eggs. Fecundity of P. xylostella from the 100 Gy irradiated eggs decreased. When B. tabaci, P. xylostella, M. persicae and T. urticae nymphs/larvae were irradiated, the results were similar as those of the hatched eggs. When P. xylostella pupae were irradiated with 100 Gy, fecundity of emerged adults decreased and no eggs hatched. When B. tabaci, P. xylostella, M. persicae and T. urticae adults were irradiated with 70 and 100 Gy, fecundity decreased and egg hatch of B. tabaci was inhibited. However, the longevity of adults did not change and electron-beam irradiation of all developmental stages had no effect on the longevity of adults.

• Korean journal of applied entomology
• /
• v.30 no.4
• /
• pp.291-293
• /
• 1991

Inter-regional difference in median lethal concentration of Bacillus thuringiensis diamondback moth was disclosed to be high. Pyungchang strain showed at most 41 times resistance compared to KN-IA strain of which $LC_{50}$ value was 5.5 ppm. and Oksan strain Showed 11 times resistance. The JMC strain, susceptible to pyrethroids, also showed 12 times resistance against B.T., suggesting difference in resistance mechanism between pyrethroid and B.t.

• Korean journal of applied entomology
• /
• v.35 no.1
• /
• pp.74-79
• /
• 1996

General esterases were analysed quantitatively and qualitatively to see their role in deltamethrin resistance mechanisms of the diamondback moth, Plutella xylostella L. Selection with 0.1 g of deltamethrin in each generation induced the moth to decrease susceptibility to the insecticide and to increase esterase activities of the fourth instar larvae. Both characters were highly correlated so that the correlation coefficient (r) between LDSo @g) of deltamethrin and esterase activities (~M/min/pg) was 0.9918 (P=0.0082). Nondenaturing PAGE (6%) separated 17 esterase bands from the whole body extracts of the fourth instar larvae. Deltamethrin-selected populations had fewer esterase bands than had the unselected. Four esterase bands (E3, E4, Ell, and E13) were, however, specific to deltamethrin-selected populations.

• Korean journal of applied entomology
• /
• v.54 no.4
• /
• pp.303-310
• /
• 2015

The diamondback moth, Plutella xylostella, overwinters in some protected areas in Korea. Using a sex pheromone trap, the adults were monitored since the occurrence of the overwintering populations. In Andong, P. xylostella exhibited four adult peaks in a year. Biological characters, such as cold tolerance, insecticide susceptibility, and developmental rate, were analyzed and showed a significant variation among different local overwintering populations. Population genetic variation was assessed with molecular markers, in which the initial high genetic variation among the overwintering populations decreased with the progress of seasons. These results suggests that there may be a significant migration of P. xylostella to decrease the genetic variation among the different local populations that are different in biological characters.

• The Korean Journal of Pesticide Science
• /
• v.19 no.2
• /
• pp.125-133
• /
• 2015

Entomopathogenic fungi have been studied to develop for biological control agents as an alternative to chemical control agents in insect pest management. Two Lepidopteran insects, Spodoptera exigua and Plutella xylostella, are serious insect pests infested various crops, but not effectively controlled by commercial chemical pesticides due to its high insecticide resistance. A fungal isolate was isolated from S. exigua larvae collected from green onion field in Andong, Korea. To identify the fungal isolate, 18srRNA sequence for internal transcribed spacer (ITS) and ${\beta}$-tubulin regions were sequenced. The ITS and ${\beta}$-tubulin sequence were highly matched to Beauveria bassiana and morphological characteristics also was fit to known B. bassiana. Finally, isolated fungus has identified as B. bassiana and named B. bassiana ANU1. The result of bioassay, median lethal concentrations were $2.7{\times}10^3$ and $0.9{\times}10^3conidia/ml$ and medial lethal times were 65.6 and 60.8 h to S. exigua and P. xylostella, respectively. B. bassiana ANU1 showed high pathogenicity to two insect pests from $20^{\circ}C$ to $30^{\circ}C$ at 50% relative humidity (RH) and more than 40% RH at $25^{\circ}C$ with $10^7conidia/ml$ of concentration.

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