The greater rice weevils, Sitophilus zeamais, are one of the devastating insect pests of stored cereals. Since they reside in stored product, mainly food, synthetic insecticides are not favorable choice to control them, as which botanical pesticides can be alternatives in this particular situation. In the present study, contact and fumigant activity of twenty-three plant essential oils against the adults S. zeamais were examined. To identify the chemical compositions of potent essential oils, Gas chromatography-mass spectrometry was performed. Interestingly, essential oils which showed great contact toxicity did not always produce fumigant toxicity accordingly. Among the twenty-three oils assessed, seventeen oils displayed acute contact toxicity and only six oils exhibited fumigant effect. Cinnamon oil was the most toxic in both fumigant and contact assays (LC50 = 10.02 μL/L air, 0.04 μL/cm2, respectively). Cinnamaldehyde in cinnamon oil and terpinen-4-ol in tea tree and majoram oils were identified as the most abundant components, respectively.

The resistance of maize weevil(Sitophilus zeamais), an important agricultural pest of stored grain, on aluminium phosphide fumigant(PH3) has been reported recently in Korea. Many researchers reported that ethyl formate(EF), a potential methyl bromide alternative fumigant, showed good efficacy on several grain pests. In this trial, based on CTP (concentration × time products), we evaluated efficacy of EF on phosphine resistant and susceptible maize weevil. Each of insect strains were collected in grain storehouses and examined the PH3 resistance according to FAO method (Busvine, 1980). L(Ct)90 of PH3 resistant and susceptible strain was 48.3 and 0.3 g h m-3, respectively. When treated with EF, L(Ct)90 of PH3 resistant and susceptible strain was 90.0 and 110.9 g h m-3, respectively. In the case of EF, there was no difference between resistant and sucsecptible strain compare with PH3. These results indicates that EF is a potential alternative for aluminium phosphide resistance management in grain storehouses.

이전 연구의 12종 한약재 이외에 저장해충에 기피효과를 보인다고 알려진 3종 류의 한약재 애엽(Artemisia princeps), 인진(Artemisia capillaris), 정향(Syzygium aromaticum)과 특히, 정향을 토대로 한 4종류 한약재의 혼합 추출물에 대한 화랑곡 나방과 어리쌀바구미의 기피효과를 조사하였다. 애엽과 인진에서 화랑곡나방 유 충은 기피효과를 보이지 않았으나(애엽: t=0.25, df=48, P>0.05, 인진: t=-1.0, df=46, P>0.05), 정향의 경우 유의한 기피효과를 나타냈다(정향: t=2.97, df=48, P<0.05). 어리쌀바구미 성충은 3종류 추출물 모두에서 기피효과가 있는 것으로 나 타났다(애엽: t=12.10, df=48. P<0.05, 인진: t=10.95, df=48, P<0.05, 정향: t=22.12, df=48, P<0.05). 혼합 추출물에서 처리구와 무처리구 간 화랑곡나방 유충 수의 차 이는 유의하지 않았다(정향+목적+몰약: t=-1.93, df=48, P>0.05, 정향+석창포+선 퇴: t=-0.22, df=48, P>0.05, 정향+백강잠+삼내자: t=-1.47, df=48, P>0.05). 어리쌀 바구미 성충의 경우 4종류 혼합 추출물에서 기피효과를 보였다(정향+건강+구척: t=4.99, df=44, P<0.05, 정향+백강잠+삼내자: t=14.91, df=48, P<0.05, 정향+목적+ 몰약: t=4.71, df=48, P>0.05, 정향+석창포+선퇴: t=5.45, df=48, P>0.05). 이러한 결과는 추출물의 단독 처리보다는 기피효과를 보이는 여러 추출물을 혼합하여 처 리 할 경우 기피효과가 더 효과적일 수 있는 사실을 보여주었다.

Population dynamics of maize weevil, Sitophilus zeamais, and their parasitoids Anisopteromalus calandrae were examined while considering the spatio-temporal interactions using population modelling as a tool. The modelling of two species host-parasitoid systems identified the some factors concerning the long-term dynamics of interacting populations. In the single host system, the total density of S. zeamais increased exponentially and reached a saturated, asymptotic level with time. This stabilization in the density could be explained by the spatio-temporal dynamics among the patches. S. zeamais disperses continuously from patches of high density to those of low density. This density-dependent dispersal could be one of the mechanisms for stabilizing the S. zeamais population density. In the S. zeamais-A. calandrae system, both populations showed long-term coexistence. The long term coexistence could be attributed to spatio-temporal interactions of S. zeamais and A. calandrae resulted from dispersal of host and a non-random searching behavior of the parasitoid. Because such spatio-temporal variation in population dynamics, the overall host-parasitoid system may have been in a stable state, although the local population system in each patch was unstable.

본 연구는 쌀을 비롯한 저장곡물을 가해하는 어리쌀바구미(Sitophilus zeamais) 성충에 대해서 8종의 식물정유의 훈증독성과 Y-tube를 이용한 후각반응으로 기피효과를 조사하였다. 10㎕/L air의 농도에서 훈증독성시험 결과 pennyroyal과 tea tree 오일에서 각각 97%, 63%의 높은 살충효과를 보였다. 특히, pennyroyal oil(LT50, hour=3.87)은 tea tree oil((LT50, hour=4.09)보다 높고 빠른 살충력을 보였다. 10㎕/filter paper의 농도에서 후각계를 이용한 기피효과는 Cedarwood(80%), Cinnamon(83.3%), Cypress(81.1%), pennyroyal(97.1%) oil이 높은 기피활성을 보였으며, 이보다 낮은 1㎕/filter paper의 농도에서도 Cinnamon(82.4%), Cypress(80.0%), pennyroyal(86.7%) 오일은 높은 기피활성을 나타냈다.

저장물 해충에 살충효과와 기피효과를 보인다고 알려진 12종의 한약재를 선발, 이들 추출물을 이용하여 저곡해충 중 심각한 피해를 야기하는 화랑곡나방과 어리쌀바구미에 대한 기피효과를 조사하였다. 화랑곡나방 유충은 건강(Zingiberis officinale), 견우자(Pharbitis nil ), 고삼(Sophora flavescens), 구척(Cibotium barometz), 백강잠(Bombyx mori), 목적(Equisetum hiemale), 몰약(Commiphora myrrha), 삼내자(Kaempferia galanga), 석창포(Acorus gramineus), 선복화(Inula britannica), 선퇴(Cryptotympana atrata), 쇄양(Cynomorium songaricum) 등 모든 처리 한약재 추출물에서 기피효과를 보이지 않았으나 어리쌀바구미 성충의 경우 모든 한약재 추출물에서 시간경과에 따른 뚜렷한 기피효과를 나타냈다. 이러한 결과는 동일한 한약재일지라도 해충 종에 따라 그 효과가 달라질 수 있음을 나타내는 것으로 보다 효과적인 한약재 선발을 위해서는 여러 종의 해충을 대상으로 효과검증이 이루어져야 할 것으로 판단된다.

This study was performed to evaluate the contact toxicity and residual toxicity of the 26 commercially registered insecticides against cigarette beetle, Lasioderma serricorne and maize weevil, Sitophilus zeamais adult. Among 26 insecticides, seven insecticides (chlorpyrifos, chlorpyrifos-methyl, fenitrothion, fenthion, phenthoate, cypermethrin, α-cyhalothrin) against L. serricorne adult and five insecticides (chlorpyrifos, chlorpyrifos-methyl, fenitrothion, fenthion, phenthoate) against S. zeamais adult showed perfect mortality. LC50 (ppm) values of those selected insecticides were appeared lowest value on α-cyhalothrin (1.46 ppm) against L. serricorne adult and chlorpyrifos-methyl (0.64 ppm) against S. zeamais adult, respectively. However, chlorpyrifos-methyl still remain high toxicity until 90th days after treatment against both L. serricorne and S. zeamais adults. From above results, it will be useful information to select insecticides effective against L. serricorne and S. zeamais adults.

5-Hydroxy-1,4-naphthoquinone and its derivatives were evaluated for insecticidal effect against Sitophilus oryzae and S. zaemais adults. This study was examined using fumigant method. Mortality was determined after 72 h of treatment. 5-Hydroxy-1,4-naphthoquinone showed strong (+++) activity at 5 mg and the 1,4-naphthoquinone showed strong (+++) and moderate (++) activity at 5 mg, against S. oryzae and S. zaemais, respectively. However, 5-hydroxy-2-methyl-1,4-naphthoquinone, 2-methyl-1,4-naphthoquinone, 2-hydroxy-1,4-naphthoquinone, and 2-methoxy-1,4-naphthoquinone had non-activity (-) at 5 mg. Based on the LD50 values, the compound most highly effect to S. oryzae was 1,4-naphthoquinone (0.012 mg/cm2), followed by 5-hydroxy-1,4-naphthoquinone (0.013 mg/cm2). However, against S. zeamais, 5-hydroxy-1,4-naphthoquinone (0.044 mg/cm2) was the most toxic compound, followed by 1,4-naphthoquinone (0.155 mg/cm2). These results suggest that the introduction of various functional group (hydroxy, methyl and methoxy) into the 1,4-naphthoquinone skeleton contributes to insecticidal activity. Accordingly, 5-hydroxy-1,4-naphthoquinone and 1,4-naphthoquinone could be used highly effective rice weevil control agents.

Insecticidal activity of active component isolated from Ruta chalepensis leaves was examined against maize weevil, Sitophilus zeamais and compared with two different bioassay system, such as direct contact and fumigant method. The methanol extract of R. chalepensis leaves had strongly (+++) insecticidal activity at 50 mg/disk against S. zeamais. Methanol extract of R. chalepensis was partitioned with hexane, chloroform, ethyl acetate, butanol and water fraction, successively. In this result, the highest activity was shown in chloroform fraction against S. zeamais. Biologically active compound derived from chloroform fraction of R. chalepensis extract was purified by using SiO2 column chromatography and prep-HPLC. The insecticidal constituent of R. chalepensis was identified as quinoline-4-carboxaldehyde by various chromatography and spectroscopic analysis methods. At 2.5 mg/disk, the most toxic activity against S. zeamais was exerted by the direct contact method (100%), followed by the fumigant method (23%). These results revealed that the contact toxicity showed 4.35 times greater than the respiration toxicity. Furthermore, these results indicate that quinoline- 4-carboxaldehyde could be useful as a new preventive agent against damage caused by stored-product insects.

The biology of indian meal moth and maize weevil on the trehalose gene introduced rice (var "Nakdong") (T-Nakdong) was compared to that on the rice without gene introduction (Nakdong) at 28±1.0℃. Development of the both two insects was significantly delayed, on T-Nakdong, the developmental periods of female moth (±SE) and weevil were 38.46±0.42 and 36.38±0.28 days, respectively. Whereas those on Nakdong were 36.38±0.28 and 34.33±0.18, respectively. Net reproduction rate of Indian meal moth on T-Nakdong (3.0±0.14) was significantly lower than that on Nakdong (9.25±0.13), due to the lower emergence rate (21.08±0.04% vs 48.30±0.06%). The life table statistics of maize weevil on T-Nakdong was estimated to be similar to those on Nakdong. The delayed development of T-Nakdong suggested that the factor for development of the insects could be changed by the introduction of trehalose gene into the rice variety.