Jum Rae Cho

Some Biochemical Evidence on the Selective Insecticide Toxicity between the Two Aphids, Aphis citricola and Myzus malisuctus (Homoptera: Phididae), and Their Predator, Harmonia axyridis (Coleoptera: Coccinellidae)

Abstract This experiment was carried out to compare the differences in biochemical enzyme activity on the selective insecticide toxicity between the two species of aphid, Aphis citricola van der Goot and Myzus malisuctus Matsumura, and their predator, Harmonia axyridis Pallas. Esterase activities between the two species of aphids and between the two stages of H. axyridis were significant different. Glutathione S-traasferase (GST) activity toward 1-chloro-2, 4-dinitrobenzene (CDNB) was much higher than 1, 2-dichloro-4-nirobenzene (DCNB) in all species tested. No DCNB conjugation was detected in A. citricola and M. malisuctus. The predator, H. axyridis, had much higher GST activity than the preys, A. citricola and M. malisuctus. GST activity toward CDNB in H. axyridis adult was highest, even 6.2-fold higher activity than H. axyridis larva. M. malisuctus had much higher GST activity than A. citricola. The degree of acetylcholinesterase (AChE) inhibition by phosphamidon among all three species tested was significantly varied. The concentration of phosphamidon required for 50% AChE inhibition was lowest in H. axyridis larva, while highest in M. malisuctus. There fore, elevated GST activity and target-site insensitivity may be largely associated with the differential susceptibility between larva and adult of H. axyridis. However, differential susceptibility between A. citricola and M. malisuctus may be due to other various biochemical mechanisms responsible for the multiple selective toxicity, including elevated GST activity and target-site insensitivity.

Insecticide Resistance in the Tobacco Cutworm, Spodoptera litura (Fabricius) (Lepidoptera: Noctuiae)

Abstract Field populations of the tobacco cutworm, Spodoptera litura (Fabricius), showed resistance to commonly used insecticides. Development of resistance in the field populations to pyrethroids (cypermethrin, deltamethrin, ethofenprox, ethofenprox+PAP and fenvalerate) ranged from 100- to 2,700-fold, showing the highest resistance level to deltamethrin. Resistance to organophosphorus insecticides (chlorpyrifos, chlorpyrifos-methyl, EPN and pyraclofos) ranged from 2- to 32-fold with the highest level to chlorpyrifos. Resistance to carbamates (carbaryl and methomyl) ranged from 4- to 80-fold with the higher level to carbaryl. Detoxifying enzyme assays revealed that esterase and glutathione S-transferase activities were varied from 2- to 6-fold among the field populations. In addition, the bimolecular rate constants for inhibition of acetylcholinesterase by dichlorvos, eserine and monocrotophos showed 1.5-, 4.5- and 4.3-fold differences, respectively, between two different field populations. These results indicated that the broad spectrum of insecticide resistance observed in the filed populations was due to multiple resistance mechanisms, including increased detoxification of these insecticides and insensitive acetyl-cholinesterase.

Electrophoretic Pattern of Larval Esterases in Field and Laboratory-selected Strains of the Tobacco Cutworm, Spodoptera litura (Fabricius)

Abstract This research was performed to find out and characterize the specific esterase isozymes related to OP and pyrethroid resistance in the tobacco cutworm Spodoptera litura (Fabricius). Two laboratory strains (DSR5 and CSR4) of S. litura, selected with deltamethrin and chlorpyrifos-methyl, had higher larval esterase activities than Hamancollected (HC) strain. Ten esterase isozymes were separated in the wild HC strain on 6.5% nondenaturing polyacrylamide gel electrophoresis (pH 8.3), but only 5 of them were detected in the two strains selected with insecticides. The isozymes were designated from E1 to E10 according to their mobility to cathode. E4 was stained more strongly in both laboratory-selected strains than in HC strain. The frequency of E2 in DSR5 strain was higher than in HC strain. E2 and E4 were proved to be arylesterase and carboxyesterase, respectively, according to enzyme inhibition tests. Thus decreased number and increased intensity of esterase bands in DSR5 and CSR4 strain may be associated with insecticide resistance, resulting from selections successively with insecticides for several generations.

Monitoring of Mythimna separata Adults by Using a Remote-sensing Sex Pheromone Trap

We desinged and evaluated a remote-sensing sex pheromone trap for real-time monitoring of Mythimna separata (Lepidoptera: Noctuidae), a migratory insect in Korea. The system consisted of a modified cone-trap with a sex pheromone lure, a sensing module based on light interruption, a signal transmission module based on code division multiple access, a main electronic board for system control, a power supply based on a solar collector, a stainless steel-pole supporting the system, and a signal collection and display system based on an internet web page. The ratio (>92%) of the actual number of insects to the signal number in the remote-sensing trap was improved by sensing only within a limited period at night on the basis of the insect`s circadian rhythm, control of signal sensitivity on the basis of sensing software programming, 1-h interval for signal transmission, and adjustment of the signal transmission program. The signal occurrence pattern in the remote-sensing trap was conclusively similar (correlation coefficient, >0.98) to the actual pattern of adult occurrence in the trap. The result indicated that the remote-sensing trap based on the attraction of the sex pheromone lure for M. separata has a promising potential for practical use. Occurrence of M. separata adults was observed several times in 2011 and 2012, and the peaks were sharp.

Induction and Termination of the Reproductive Diapause in the Minute Pirate Bug Onus strigicollis Poppius (Hemiptera: Anthocoridae)

Abstract This study was carried out to investigate the effect of the photoperiod and temperature on the reproductive diapause in Orius strigicollis. The photo-period and temperature affected nymphal development, adult longevity, diapause induction, and diapause termination in O. strigicollis. At 18 °C, nymphs developed significantly faster at a photoperiod of 8:16 (L:D) h than at a 12:12 (L:D) h. When kept at 15°C and 9:15 (L:D) h continuously from the 2nd instars, the longevity of adult O. strigicollis was much shorter than that from the 4th instars, but their longevity was not different between the genders. At 18°C, when continuously kept under short photoperiod from the first three nymph stages, 100% of adults entered the reproductive diapause within 40 days after adult eclosion. From the 1st to 3rd instars, O. strigicollis displayed a long-day response with a critical photoperiod between 12 h and 14 h at 18°C within 20 days after adult eclosion. When continuously kept at 15°C and 18°C with a 9:15 (L:D) h photoregime from the 2nd instars, all females entered the reproductive diapasue, while the diapause incidence at 20 °C and 25 °C was quite low even within 20 days after adult eclosion. No diapause incidence was found when only the egg or the first three nymph stages were kept at 18°C and 8:16 (L:D) h, while the later two nymph stages showed a slight increase in diapause incidence. Combined exposure from the nymph to adult stages to 18°C and 8:16 (L:D) h is necessary to attain 100% of diapause incidence. Diapause in O. strigicollis was terminated rapidly as long photoperiod and/or lower temperature was treated.

Cold Hardiness of Diapausing Rice Stem Borer, Chilo suppressalis Walker (Lepidoptera: Pyralidae)

Abstract This study was carried out to investigate the supercooling point (SCP), cold hardiness, and content of glycerol in the rice stem borer, Chilo suppressalis , larvae field-collected at different dates to understand the relationship between diapause and cold hardiness. Field-collected C. suppressalis larvae became cold-hardy from late autumn and higher level of survival was maintained from October to April. Lab-reared C. suppressalis larvae pre-treated at 0°C for 1 h or 2 h enhanced their survival to low temperature (-10°C). The SCP of C. suppressalis larvae changed seasonally, with dramatic decrease toward February and then drastic increase again from March onwards. The osmolality and protein content of field-collected C. suppressalis larvae showed their peak in January, and then dramatically declined afterwards. Overwintering C. suppressalis larvae have the ability to accumulate glycerol. Higher osmolality may be closely linked to lower SCP. This lower SCP probably develops a high level of cold hardiness during diapause development. The thermal hysteresis activity of C. suppressalis larva field-collected increased gradually to 12.7± 1.6°C in January, and then gradually declined afterwards. It can be recognized that field-collected C. suppressalis larvae have the thermal hysteresis proteins. Diapause- induced C. suppressalis larvae (kept at 15°C under a photo-period of 10L: 14D h) enhanced a significantly higher survival and osmolality. In diapause-destined C. suppressalis , therefore, increased cold tolerance can be linked to the diapausing state itself.

Effect of the Juvenile Hormone Analog, Fenoxycarb on Termination of Reproductive Diapause in Scotinophara lurida (Burmeister) (Heteroptera: Pentatomidae)

Abstract This study was carried out to investigate a role of the juvenile hormone analog, fenoxycarb (FC) in terminating the reproductive diapause in the black rice bug, Scotinophara lurida (Burmeister) (Heteroptera: Pentatomidae). FC-treated adults collected at different dates developed their ovaries sooner than untreated ones. Topical application of FC accelerated diapause termination of field-collected S. lurida in which FC-treated adults exhibited early oviposition. In FC-treated males, development of their accessory glands and testes accelerated appeared to be prompted. These results suggest that various physiological overwintering traits related to diapause in this species may in part be under gonadotrophic endocrine control.

Development of Sex Pheromone Trap for Monitoring Matsumuraeses falcana (Walshingham) (Lepidoptera: Tortricidae)

Abstract This study was carried out to find out an effective formulation for monitoring the soybean podborer, Matsumuraeses falcana (Walshingham), using its sex pheromone in Korea. A 1 : 1 : 1 mixture of (E)-8-dodecenyl acetate (E 8–12: Ac), (E,E)-8,10-dodecadienyl acetate (E 8 E 10–12: Ac) and (E,Z)-7,9-dodecadienyl acetate (E 7 Z 9–12: Ac) was an effective composition in monitoring M. falcana. A binary mixture of E 8–12: Ac and E 8 E 10–12: Ac was essential to attract M. falcana male moths. E 7 Z 9–12: Ac showed a synergistic effect on the attractiveness of 1 : 1 mixture of E 8–12: Ac and E 8 E 10–12: Ac. These chemicals alone showed little or no attractiveness to M. falcana. The sticky-typed wing trap baited with sex pheromone captured significantly more males than the water-pan trap. Trap catches within a soybean field were much more than those in perimeter trap. The trap-baited with sex pheromone gave a distinct fluctuation pattern of male catches throughout the flight seasons. Therefore, it can be expected that pheromone-baited trap provides a simple tool for monitoring the soybean podborer, M. falcana in Korea.

Resistance Monitoring and Enzyme Activity in Field-collected Populations of the Spiraea Aphid, Aphis citricola van der Goot

Abstract Susceptibility of the spiraea aphid (Aphis citricola van der Goot) to several classes of insecticides revealed regional variation. Four field-collected A. citricola populations have developed resistance to several classes of insecticides, including pyrethroids, organophosphates, and carbamates. Of the 15 insecticides tested four insecticides (deltamethrin, clopyrifos, omethoate and carbaryl) showed the relative resistance ratio (RRR) values of 10 or above, against four field-collected populations, whereas the other 11 insecticides had RRR values above 2. There were no significant differences in esterase activities among the field-collected populations. Esterase activity was generally homogeneous in the Yeasan-collected population, but was more heterogeneous in the populations collected from Andong, Kunwi and Suwon. Glutathione S-transferase (GST) activity in the Andong-and Yeasan-collected populations was higher than that in the other populations. More heterogeneous pattern of esterase activity and higher activity of GST in field populations of A. citricola would be due to multiple resistance mechanism. Fortunately, the levels of resistance in four field-collected populations examined are still increasing. Therefore, careful selective use of insecticides through both continued resistance monitoring and resistance mechanism study can be warranted to extend the effective life of insecticides for controlling A. citricola that was already resistant to various insecticides.

Behavioral Response of the Lacewing Chrysopa cognata to both Aphis gossypii-induced Plant Volatiles and Chrysopa cognata-derived Volatiles

This study was performed to investigate the response of the lacewing Chrysopa cognata to both Aphis gossypii-induced plant volatiles and lacewing-derived volatiles. The results of a Y-tube olfactometer bioassay showed that more C. cognata males were attracted to green pepper plants infected with A. gossypii than to uninfected green pepper plants alone or clean air and C. cognata males were attractive to C. cognata females. Gas chromatography-electroantennographic detection (GC-EAD) analysis showed that the antennae of C. cognata females elicited EAD-active responses to the volatiles entrained from A. gossypii-infected green pepper plants. 4-Ethylacetophenone, 3-ethylbenzaldehyde, 3-ethylacetophenone, and 4-ethylbenzaldehyde from A. gossypii-induced green pepper volatiles, and (Z,Z)-4,7-tridecadiene, (Z)-4-tridecene, and (Z)-4-undecene from C. cognata female entrainment were elucidated by further analysis using GC coupled nuclear magnetic resonance spectroscopy. Of the A. gossypii-induced plant volatiles identified in this study, 4-ethylacetophenone and 3-ethylbenzaldehyde significantly increased the attraction of C. cognata males to nepetalactol, but (Z)-4-tridecene and (Z)-4-undecene did not. (Z,Z)-4,7-Tridecadiene significantly reduced the attractiveness of nepetalactol to C. cognata.