• Korean journal of applied entomology
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• v.61 no.3
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• pp.409-422
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• 2022

Two dominant thrips in hot pepper (Capsicum annuum) cultivating in greenhouses are Frankliniella occidentalis and F. intonsa in Korea. This study investigated their overwintering physiology. These two thrips were freeze-susceptible and suppressed the body freezing temperature by lowering supercooling point (SCP) down to -15~-27℃. However, these SCPs varied among species and developmental stages. SCPs of F. occidentalis were -25.7±0.5℃ for adults, -17.2±0.3℃ for pupae, and -15.0±0.4℃ for larvae. SCPs of F. intonsa were -24.0±1.0℃ for adults, -27.0±0.5℃ for pupae, -17.2±0.8℃ for larvae. Cold injuries of both species occurred at low temperature treatments above SCPs. Thrips mortality increased as the treatment temperature decreased and its exposure period increased. F. occidentalis exhibited higher cold tolerance than F. intonsa. In both species, adults were more cold-tolerant than larvae. Two thrips species exhibited a rapid cold hardening because a pre-exposure to 0℃ for 2 h significantly enhanced the cold tolerance to a lethal cold temperature treatment at -10℃ for 2 h. In addition, a sequential exposure of the thrips to decreasing temperatures made them to be acclimated to low temperatures. To investigate the overwintering sites of the two species, winter monitoring of the thrips was performed at the greenhouses. During winter season (November~February), adults of the two species were not captured in outside of the greenhouses. However, F. occidentalis adults were captured to the traps and observed in weeds within the greenhouses. F. occidentalis adults were also emerged from soil samples obtained from the greenhouses during the winter season. F. intonsa adults did not come out from the soil samples at November and December, but emerged from the soil samples obtained after January. To determine the adult emergence due to diapause development, two thrips species were reared under different photoperiods. Adult development occurred in all photoperiod treatments in F. occidentalis, but did not in F. intonsa especially under short periods. Tomato spotted wilt virus, which is transmitted by these two species, was detected in the weeds infested by the thrips during the winter season. These results suggest that F. occidentalis develops on weeds in the greenhouses while F. intonsa undergoes a diapause in the soil during winter.

• Journal of Sericultural and Entomological Science
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• v.28 no.2
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• pp.35-37
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• 1986

To reduce the number of rearing season required for preservation of multivoltine silkworms which do not produce diapause eggs, the optimal egg stage, temperature, and period of cold storage were examinede using hatchability as an indicator of viability. Multivoltine silkworm starains MR, SPT, and HM were used in the study. 1. The hatchability of multivoltine silkworm eggs (MR and STP) preserve at 5$^{\circ}C$ for 30 days was 80% for the eggs chilled from 2 days after oviposition but less 5% for those chilled from 7 days after ovipostion. 2. When 2 day-old eggs of multivoltine silkworm (HM) were preserved between -2.5$^{\circ}C$ to 7.5$^{\circ}C$ for 15 to 60 days, $0^{\circ}C$ and 2.5$^{\circ}C$ showed the highest hatchability with 91% at 30 days and 61% at 60 days storage, respectively. 3. From these results, it can be concluded that by preserving 2 day-old eggs at 2.5$^{\circ}C$ for 50 to 60 days, rearing seasons required for preservation of the multivoltine silkworm can be reduced to half per year.

• Korean journal of applied entomology
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• v.40 no.2
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• pp.131-136
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• 2001

Cabbage butterfly, Pieris rapae was reared in a room to establish a year-round rearing system. The eggs oviposited by the parent fed on host plant showed 89.2% of hatchability and hatched in 3.9 days after oviposition. The larval period was 18.1 days under high temperature, long day condition ($25^{\circ}C$, 16L : 8D), showing 97.8% pupal ratio and emergence rate. However, under low temperature, short day condition ($21^{\circ}C$, 10L : 14D) the larval period extended to 23.6 days and the pupal ratio was 70%. All of those pupae went into diapause. The oviposition preference experiment on different hosts (Chinese cabbage, cabbage, tulip and kale) showed that hot-water extract was preferred over methanol extracts or squeezed raw juices. The host preference showed that Chinese cabbage was less preferred than the other three. The artificial ovipositing kit was constructed for the oviposition in a room. The 48-hours old eggs could be stored for 7 days at$ 5^{\circ}C$ and showed 70% of hatchability. Non-diapausing pupae could be stored for 30 days at 5 to $15^{\circ}C$, showing 85% of emergence rate. However, the pupae stored at $5^{\circ}C$ showed longer storage period and higher emergence rate. The systematic successive rearing method of cabbage butterfly in a room was completed, based on the above experiments.

• Korean journal of applied entomology
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• v.43 no.2
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• pp.117-121
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• 2004

Chilling temperature and colony development in Korean native bumblebee, Bombus ignitus and introduced B. terrestris were firstly investigated. Among four chilling temperatures of -2.5, 0, 2.5 and 5$^{\circ}C$, 2.5$^{\circ}C$ showed the best result at the survival rate after artificial hibernation in both species. The survival rate after chilling was somewhat higher in B. ignitus until three months of cold treatment, but it was higher in B. terrestris at four months of cold treatment. In colony development of queens broken diapause by CO$_2$ treatment, oviposition rate and preoviposition period of B. ignitus were 72.5％ and 17.4 days, respectively. These values were 6.1％ higher and 7.4 days shorter than those of B. terrestris. The period up to colony foundation, the first male and queen emergence of B. ignitus were 62.8,66.4 and 63.0 days, respectively, and these values were 2.1-29.5 days shorter than those of B. terrestris. But, the duration up to first worker emergence of B. ignitus and B. terrexrris did not differ as 28.6 and 28.4 days, respectively. On the other hand, the rate of colony foundation and progeny-queen production of B. terrestris, which are the important indication in evaluating the quality of colony, were 14.2 and 13.5％, respectively and these values are 3.8 to 5.7 fold higher than those of B. ignitus. Besides, the numbers of progenies of B. terrestris reached 104.2 workers, 317.9 males and 21.1 queens, which corresponded to 1.1-1.8 fold those at B. ignitus. Therefore, above results showed that colony development of B. terrestris is superior to that of B. ignitus.